Only list MCP tools once, not at every agent run step #3227
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This is going to break my applications. My MCP servers change their tools based on state. This is by design. The MCP protocol allows this. This will cause the agent to see tools that aren't actually available, or to not see tools that are available. |
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@phemmer Thanks for keeping a close eye on potentially breaking changes! I'll revert this in favor of a flag on the |
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You can cache, but to properly do so, you have to invalidate the cache on reconnect, or on a tool change notification. Though a flag might be good for broken mcp servers which change tools without notifications
…On October 22, 2025 2:33:14 PM EDT, Douwe Maan ***@***.***> wrote:
DouweM left a comment (pydantic/pydantic-ai#3227)
@phemmer Thanks for keeping a close eye on potentially breaking changes! I'll revert this in favor of a flag on the `MCPServer`, and we'll keep the current behavior by default.
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#3227 (comment)
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@phemmer Yep we should subscribe to those notifications at the very least. |
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Closes #3218
cc @Kludex as you also requested this