diff --git a/src/Agents/CompositeAIContextProvider.cs b/src/Agents/CompositeAIContextProvider.cs
new file mode 100644
index 0000000..ca0d181
--- /dev/null
+++ b/src/Agents/CompositeAIContextProvider.cs
@@ -0,0 +1,52 @@
+using Microsoft.Agents.AI;
+using Microsoft.Extensions.AI;
+
+namespace Devlooped.Agents.AI;
+
+/// <summary>
+/// Concatenates multiple <see cref="AIContext"/> instances into a single one.
+/// </summary>
+class CompositeAIContextProvider : AIContextProvider
+{
+    readonly AIContext context;
+
+    public CompositeAIContextProvider(IList<AIContext> contexts)
+    {
+        if (contexts.Count == 1)
+        {
+            context = contexts[0];
+            return;
+        }
+
+        // Concatenate instructions from all contexts
+        context = new();
+        var instructions = new List<string>();
+        var messages = new List<ChatMessage>();
+        var tools = new List<AITool>();
+
+        foreach (var ctx in contexts)
+        {
+            if (!string.IsNullOrEmpty(ctx.Instructions))
+                instructions.Add(ctx.Instructions);
+
+            if (ctx.Messages != null)
+                messages.AddRange(ctx.Messages);
+
+            if (ctx.Tools != null)
+                tools.AddRange(ctx.Tools);
+        }
+
+        // Same separator used by M.A.AI for instructions appending from AIContext
+        if (instructions.Count > 0)
+            context.Instructions = string.Join('\n', instructions);
+
+        if (messages.Count > 0)
+            context.Messages = messages;
+
+        if (tools.Count > 0)
+            context.Tools = tools;
+    }
+
+    public override ValueTask<AIContext> InvokingAsync(InvokingContext context, CancellationToken cancellationToken = default)
+        => ValueTask.FromResult(this.context);
+}
\ No newline at end of file
diff --git a/src/Agents/ConfigurableAIAgent.cs b/src/Agents/ConfigurableAIAgent.cs
index 4701ad7..818a684 100644
--- a/src/Agents/ConfigurableAIAgent.cs
+++ b/src/Agents/ConfigurableAIAgent.cs
@@ -113,7 +113,45 @@ public override IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(IEnum
                 services.GetService<AIContextProviderFactory>();
 
             if (contextFactory is not null)
+            {
+                if (options.Use?.Count > 0)
+                    throw new InvalidOperationException($"Invalid simultaneous use of keyed service {nameof(AIContextProviderFactory)} and '{section}:use' in configuration.");
+
                 options.AIContextProviderFactory = contextFactory.CreateProvider;
+            }
+            else if (services.GetKeyedService<AIContextProvider>(name) is { } contextProvider)
+            {
+                if (options.Use?.Count > 0)
+                    throw new InvalidOperationException($"Invalid simultaneous use of keyed service {nameof(AIContextProvider)} and '{section}:use' in configuration.");
+
+                options.AIContextProviderFactory = _ => contextProvider;
+            }
+            else if (options.Use?.Count > 0)
+            {
+                var contexts = new List<AIContext>();
+                foreach (var use in options.Use)
+                {
+                    var context = services.GetKeyedService<AIContext>(use);
+                    if (context is null)
+                    {
+                        var function = services.GetKeyedService<AITool>(use) ??
+                            services.GetKeyedService<AIFunction>(use) ??
+                            throw new InvalidOperationException($"Specified AI context '{use}' for agent '{name}' is not registered as either an {nameof(AIContent)} or an {nameof(AITool)}.");
+
+                        contexts.Add(new AIContext { Tools = [function] });
+                    }
+                    else
+                    {
+                        contexts.Add(context);
+                    }
+                }
+
+                options.AIContextProviderFactory = _ => new CompositeAIContextProvider(contexts);
+            }
+        }
+        else if (options.Use?.Count > 0)
+        {
+            throw new InvalidOperationException($"Invalid simultaneous use of {nameof(ChatClientAgentOptions)}.{nameof(ChatClientAgentOptions.AIContextProviderFactory)} and '{section}:use' in configuration.");
         }
 
         if (options.ChatMessageStoreFactory is null)
@@ -148,6 +186,7 @@ void OnReload(object? state)
     internal class AgentClientOptions : ChatClientAgentOptions
     {
         public string? Client { get; set; }
+        public IList<string>? Use { get; set; }
     }
 }
 
diff --git a/src/Tests/ConfigurableAgentTests.cs b/src/Tests/ConfigurableAgentTests.cs
index 66f542d..ab10616 100644
--- a/src/Tests/ConfigurableAgentTests.cs
+++ b/src/Tests/ConfigurableAgentTests.cs
@@ -6,6 +6,7 @@
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
 using Moq;
+using Tomlyn.Extensions.Configuration;
 
 namespace Devlooped.Agents.AI;
 
@@ -178,34 +179,6 @@ public void CanReloadConfiguration()
         Assert.Equal("xai", agent.GetService<AIAgentMetadata>()?.ProviderName);
     }
 
-    [Fact]
-    public void AssignsContextProviderFromKeyedService()
-    {
-        var builder = new HostApplicationBuilder();
-        var context = Mock.Of<AIContextProvider>();
-
-        builder.Services.AddKeyedSingleton<AIContextProviderFactory>("bot",
-            Mock.Of<AIContextProviderFactory>(x
-                => x.CreateProvider(It.IsAny<ChatClientAgentOptions.AIContextProviderFactoryContext>()) == context));
-
-        builder.Configuration.AddInMemoryCollection(new Dictionary<string, string?>
-        {
-            ["ai:clients:chat:modelid"] = "gpt-4.1-nano",
-            ["ai:clients:chat:apikey"] = "sk-asdfasdf",
-            ["ai:agents:bot:client"] = "chat",
-            ["ai:agents:bot:options:temperature"] = "0.5",
-        });
-
-        builder.AddAIAgents();
-
-        var app = builder.Build();
-        var agent = app.Services.GetRequiredKeyedService<AIAgent>("bot");
-        var options = agent.GetService<ChatClientAgentOptions>();
-
-        Assert.NotNull(options?.AIContextProviderFactory);
-        Assert.Same(context, options?.AIContextProviderFactory?.Invoke(new ChatClientAgentOptions.AIContextProviderFactoryContext()));
-    }
-
     [Fact]
     public void AssignsContextProviderFromService()
     {
@@ -350,12 +323,248 @@ public void CanSetGrokOptions()
     }
 
     [Fact]
-    public void Task()
+    public void UseContextProviderFactoryFromKeyedService()
+    {
+        var builder = new HostApplicationBuilder();
+        var context = Mock.Of<AIContextProvider>();
+
+        builder.Services.AddKeyedSingleton<AIContextProviderFactory>("bot",
+            Mock.Of<AIContextProviderFactory>(x
+                => x.CreateProvider(It.IsAny<ChatClientAgentOptions.AIContextProviderFactoryContext>()) == context));
+
+        builder.Configuration.AddInMemoryCollection(new Dictionary<string, string?>
+        {
+            ["ai:clients:chat:modelid"] = "gpt-4.1-nano",
+            ["ai:clients:chat:apikey"] = "sk-asdfasdf",
+            ["ai:agents:bot:client"] = "chat",
+            ["ai:agents:bot:options:temperature"] = "0.5",
+        });
+
+        builder.AddAIAgents();
+
+        var app = builder.Build();
+        var agent = app.Services.GetRequiredKeyedService<AIAgent>("bot");
+        var options = agent.GetService<ChatClientAgentOptions>();
+
+        Assert.NotNull(options?.AIContextProviderFactory);
+        Assert.Same(context, options?.AIContextProviderFactory?.Invoke(new ChatClientAgentOptions.AIContextProviderFactoryContext()));
+    }
+
+    [Fact]
+    public async Task UseContextProviderFromKeyedServiceAsync()
+    {
+        var builder = new HostApplicationBuilder();
+        var context = new AIContext();
+
+        var provider = new Mock<AIContextProvider>();
+        provider
+            .Setup(x => x.InvokingAsync(It.IsAny<AIContextProvider.InvokingContext>(), default(CancellationToken)))
+            .ReturnsAsync(context);
+
+        builder.Services.AddKeyedSingleton("chat", provider.Object);
+
+        builder.Configuration.AddToml(
+            """"
+            [ai.clients.openai]
+            modelid = "gpt-4.1"
+            apikey = "sk-asdf"
+            
+            [ai.agents.chat]
+            description = "Chat agent."
+            client = "openai"
+            """");
+
+        builder.AddAIAgents();
+
+        var app = builder.Build();
+        var agent = app.Services.GetRequiredKeyedService<AIAgent>("chat");
+        var options = agent.GetService<ChatClientAgentOptions>();
+
+        Assert.NotNull(options?.AIContextProviderFactory);
+
+        var actualProvider = options?.AIContextProviderFactory?.Invoke(new());
+
+        Assert.NotNull(actualProvider);
+
+        Assert.Same(context, await actualProvider.InvokingAsync(new([]), default));
+    }
+
+    [Fact]
+    public void UseAndContextProviderFactoryIncompatible()
     {
-        var agent = new AgentRunResponse() { AgentId = "agent-123" };
-        var chat = agent.AsChatResponse();
+        var builder = new HostApplicationBuilder();
+
+        builder.Configuration.AddToml(
+            """"
+            [ai.clients.openai]
+            modelid = "gpt-4.1"
+            apikey = "sk-asdf"
+
+            [ai.agents.chat]
+            description = "Chat agent."
+            client = "openai"
+            use = ["voseo"]
+
+            [ai.context.voseo]
+            instructions = """\
+                Default to using spanish language, using argentinean "voseo" in your responses \
+                (unless the user explicitly talks in a different language). \
+                This means using "vos" instead of "tú" and conjugating verbs accordingly. \
+                Don't use the expression "pa'" instead of "para". Don't mention the word "voseo".
+                """            
+            """");
+
+        builder.AddAIAgents(configureOptions: (name, options)
+            => options.AIContextProviderFactory = context => Mock.Of<AIContextProvider>());
+
+        var app = builder.Build();
+
+        var exception = Assert.ThrowsAny<Exception>(() => app.Services.GetRequiredKeyedService<AIAgent>("chat"));
+
+        Assert.Contains("ai:agents:chat:use", exception.Message);
+    }
+
+    [Fact]
+    public void UseAndContextProviderIncompatible()
+    {
+        var builder = new HostApplicationBuilder();
+
+        builder.Configuration.AddToml(
+            """"
+            [ai.clients.openai]
+            modelid = "gpt-4.1"
+            apikey = "sk-asdf"
+
+            [ai.agents.chat]
+            description = "Chat agent."
+            client = "openai"
+            use = ["voseo"]
+
+            [ai.context.voseo]
+            instructions = """\
+                Default to using spanish language, using argentinean "voseo" in your responses \
+                (unless the user explicitly talks in a different language). \
+                This means using "vos" instead of "tú" and conjugating verbs accordingly. \
+                Don't use the expression "pa'" instead of "para". Don't mention the word "voseo".
+                """            
+            """");
+
+        builder.Services.AddKeyedSingleton("chat", Mock.Of<AIContextProvider>());
+        builder.AddAIAgents();
+
+        var app = builder.Build();
+        var exception = Assert.ThrowsAny<Exception>(() => app.Services.GetRequiredKeyedService<AIAgent>("chat"));
+
+        Assert.Contains("ai:agents:chat:use", exception.Message);
+    }
+
+    [Fact]
+    public async Task UseAIContextFromKeyedServiceAsync()
+    {
+        var builder = new HostApplicationBuilder();
+        var voseo = new AIContext { Instructions = "voseo" };
+
+        builder.Configuration.AddToml(
+            """"
+            [ai.clients.openai]
+            modelid = "gpt-4.1"
+            apikey = "sk-asdf"
+            
+            [ai.agents.chat]
+            description = "Chat agent."
+            client = "openai"
+            use = ["voseo"]
+            """");
+
+        builder.Services.AddKeyedSingleton("voseo", voseo);
+
+        builder.AddAIAgents();
+
+        var app = builder.Build();
+        var agent = app.Services.GetRequiredKeyedService<AIAgent>("chat");
+        var options = agent.GetService<ChatClientAgentOptions>();
+
+        Assert.NotNull(options?.AIContextProviderFactory);
+        var actualProvider = options?.AIContextProviderFactory?.Invoke(new());
+        Assert.NotNull(actualProvider);
+
+        var actualContext = await actualProvider.InvokingAsync(new([]), default);
+
+        Assert.Same(voseo, await actualProvider.InvokingAsync(new([]), default));
+    }
+
+    [Fact]
+    public async Task UseAggregatedAIContextsFromKeyedServiceAsync()
+    {
+        var builder = new HostApplicationBuilder();
+        var voseo = new AIContext { Instructions = "voseo" };
+        var formatting = new AIContext { Instructions = "formatting" };
+
+        builder.Configuration.AddToml(
+            """"
+            [ai.clients.openai]
+            modelid = "gpt-4.1"
+            apikey = "sk-asdf"
+            
+            [ai.agents.chat]
+            description = "Chat agent."
+            client = "openai"
+            use = ["voseo", "formatting"]
+            """");
+
+        builder.Services.AddKeyedSingleton("voseo", voseo);
+        builder.Services.AddKeyedSingleton("formatting", formatting);
+
+        builder.AddAIAgents();
+
+        var app = builder.Build();
+        var agent = app.Services.GetRequiredKeyedService<AIAgent>("chat");
+        var options = agent.GetService<ChatClientAgentOptions>();
+
+        Assert.NotNull(options?.AIContextProviderFactory);
+        var actualProvider = options?.AIContextProviderFactory?.Invoke(new());
+        Assert.NotNull(actualProvider);
+
+        var actualContext = await actualProvider.InvokingAsync(new([]), default);
+
+        Assert.StartsWith(voseo.Instructions, actualContext.Instructions);
+        Assert.EndsWith(formatting.Instructions, actualContext.Instructions);
+    }
+
+    [Fact]
+    public async Task UseAIToolFromKeyedServiceAsync()
+    {
+        var builder = new HostApplicationBuilder();
+
+        builder.Configuration.AddToml(
+            """"
+            [ai.clients.openai]
+            modelid = "gpt-4.1"
+            apikey = "sk-asdf"
+            
+            [ai.agents.chat]
+            description = "Chat agent."
+            client = "openai"
+            use = ["get_date"]
+            """");
+
+        AITool tool = AIFunctionFactory.Create(() => DateTimeOffset.Now, "get_date");
+        builder.Services.AddKeyedSingleton("get_date", tool);
+        builder.AddAIAgents();
+
+        var app = builder.Build();
+        var agent = app.Services.GetRequiredKeyedService<AIAgent>("chat");
+        var options = agent.GetService<ChatClientAgentOptions>();
+
+        Assert.NotNull(options?.AIContextProviderFactory);
+        var provider = options?.AIContextProviderFactory?.Invoke(new());
+        Assert.NotNull(provider);
+
+        var context = await provider.InvokingAsync(new([]), default);
 
-        Assert.Equal("agent-123", chat.AdditionalProperties!["AgentId"]);
+        Assert.NotNull(context.Tools);
+        Assert.Single(context.Tools);
+        Assert.Same(tool, context.Tools[0]);
     }
 }
 
diff --git a/src/Tests/Extensions/Configuration.cs b/src/Tests/Extensions/Configuration.cs
index a8f0d29..17a2e04 100644
--- a/src/Tests/Extensions/Configuration.cs
+++ b/src/Tests/Extensions/Configuration.cs
@@ -1,10 +1,15 @@
 using System.Reflection;
+using System.Text;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Options;
+using Tomlyn.Extensions.Configuration;
 
 public static class ConfigurationExtensions
 {
+    public static IConfigurationBuilder AddToml(this IConfigurationBuilder builder, string contents)
+        => builder.AddTomlStream(new MemoryStream(Encoding.UTF8.GetBytes(contents)));
+
     public static IConfiguration Configuration { get; } = new ConfigurationBuilder()
         .AddEnvironmentVariables()
         .AddUserSecrets(Assembly.GetExecutingAssembly())
diff --git a/src/Tests/Tests.csproj b/src/Tests/Tests.csproj
index b7e726d..0244853 100644
--- a/src/Tests/Tests.csproj
+++ b/src/Tests/Tests.csproj
@@ -5,6 +5,7 @@
     <NoWarn>OPENAI001;$(NoWarn)</NoWarn>
     <LangVersion>Preview</LangVersion>
     <EmitCompilerGeneratedFiles>true</EmitCompilerGeneratedFiles>
+    <RootNamespace>Devlooped</RootNamespace>
   </PropertyGroup>
 
   <ItemGroup>
@@ -24,6 +25,8 @@
     <PackageReference Include="Microsoft.Extensions.Http.Resilience" Version="9.10.0" />
     <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" Version="9.0.10" />
     <PackageReference Include="Microsoft.Extensions.Logging.Console" Version="9.0.10" />
+
+    <PackageReference Include="Tomlyn.Extensions.Configuration" Version="1.0.6" />
   </ItemGroup>
 
   <ItemGroup>
@@ -38,8 +41,10 @@
   </ItemGroup>
 
   <ItemGroup>
+    <None Update=".env" CopyToOutputDirectory="PreserveNewest" />
     <None Update="Content\**\*.*" CopyToOutputDirectory="PreserveNewest" />
     <Content Update="Content\**\*.*" CopyToOutputDirectory="PreserveNewest" />
+    <Content Include="*.json;*.ini;*.toml" Exclude="@(Content)" CopyToOutputDirectory="PreserveNewest" />
   </ItemGroup>
 
 </Project>