fix: transform MCP tool schemas for Google/Gemini compatibility

[ZGltYQ]

• Apply ProviderTransform.schema() to MCP tools to convert integer enums to strings
• Convert function declaration to arrow function for strict mode compliance
• Fix variable shadowing in content iteration loop

Resolves 'Invalid value at tools.function_declarations' error when using
Google/Gemini with MCP tools that have integer enum parameters.

Closes: #4512

[rekram1-node]

We need this but I tested with several providers and this does not work correctly. Your changes will basically delete the input schema entirely

I'd recommend not using type error silencing because it is going to make code harder to maintain.

[ZGltYQ]

Fixed. I have tested it with grok, anthropic, gemini etc.

[rekram1-node]

This looks good ill test more tmr just to be sure.

We used to sanitize the tools way better before we did the zodv4 migration and then we kinda just forgot about it ig:

function sanitizeGeminiParameters(schema: z.ZodTypeAny, visited = new Set()): z.ZodTypeAny {
    if (!schema || visited.has(schema)) {
      return schema
    }
    visited.add(schema)

    if (schema instanceof z.ZodDefault) {
      const innerSchema = schema.removeDefault()
      // Handle Gemini's incompatibility with `default` on `anyOf` (unions).
      if (innerSchema instanceof z.ZodUnion) {
        // The schema was `z.union(...).default(...)`, which is not allowed.
        // We strip the default and return the sanitized union.
        return sanitizeGeminiParameters(innerSchema, visited)
      }
      // Otherwise, the default is on a regular type, which is allowed.
      // We recurse on the inner type and then re-apply the default.
      return sanitizeGeminiParameters(innerSchema, visited).default(schema._def.defaultValue())
    }

    if (schema instanceof z.ZodOptional) {
      return z.optional(sanitizeGeminiParameters(schema.unwrap(), visited))
    }

    if (schema instanceof z.ZodObject) {
      const newShape: Record<string, z.ZodTypeAny> = {}
      for (const [key, value] of Object.entries(schema.shape)) {
        newShape[key] = sanitizeGeminiParameters(value as z.ZodTypeAny, visited)
      }
      return z.object(newShape)
    }

    if (schema instanceof z.ZodArray) {
      return z.array(sanitizeGeminiParameters(schema.element, visited))
    }

    if (schema instanceof z.ZodUnion) {
      // This schema corresponds to `anyOf` in JSON Schema.
      // We recursively sanitize each option in the union.
      const sanitizedOptions = schema.options.map((option: z.ZodTypeAny) => sanitizeGeminiParameters(option, visited))
      return z.union(sanitizedOptions as [z.ZodTypeAny, z.ZodTypeAny, ...z.ZodTypeAny[]])
    }

    if (schema instanceof z.ZodString) {
      const newSchema = z.string({ description: schema.description })
      const safeChecks = ["min", "max", "length", "regex", "startsWith", "endsWith", "includes", "trim"]
      // rome-ignore lint/suspicious/noExplicitAny: <explanation>
      ;(newSchema._def as any).checks = (schema._def as z.ZodStringDef).checks.filter((check) =>
        safeChecks.includes(check.kind),
      )
      return newSchema
    }

    return schema
  }

  function optionalToNullable(schema: z.ZodTypeAny): z.ZodTypeAny {
    if (schema instanceof z.ZodObject) {
      const shape = schema.shape
      const newShape: Record<string, z.ZodTypeAny> = {}

      for (const [key, value] of Object.entries(shape)) {
        const zodValue = value as z.ZodTypeAny
        if (zodValue instanceof z.ZodOptional) {
          newShape[key] = zodValue.unwrap().nullable()
        } else {
          newShape[key] = optionalToNullable(zodValue)
        }
      }

      return z.object(newShape)
    }

    if (schema instanceof z.ZodArray) {
      return z.array(optionalToNullable(schema.element))
    }

    if (schema instanceof z.ZodUnion) {
      return z.union(
        schema.options.map((option: z.ZodTypeAny) => optionalToNullable(option)) as [
          z.ZodTypeAny,
          z.ZodTypeAny,
          ...z.ZodTypeAny[],
        ],
      )
    }

    return schema
  }