fix: Make context logging functions spec-compliant - Fixes #397

[akshay-kumar-bm]

Fixes #397 - FastMCP Context logging methods now accept Any type instead of restricting to str, aligning with MCP specification requirements.

Motivation and Context

The MCP specification requires logging functions to accept any JSON-serializable data (Any type), but FastMCP's Context.log() only accepted strings. This prevented users from logging structured data like dictionaries, lists, numbers, and booleans.

How Has This Been Tested?

• Added comprehensive test test_context_logging_with_structured_data covering all JSON types (dict, list, number, boolean, string)
• All existing 84 tests pass
• Verified backward compatibility with string messages
• Tested with mock assertions to confirm correct data types passed to underlying session

Breaking Changes

Yes - Removed the extra parameter from all logging methods:

• Before: ctx.info("message", extra={"key": "value"})
• After: ctx.info({"message": "message", "key": "value"})

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

Changed Context.log() signature from message: str, extra: dict to data: Any. The extra parameter was not part of the MCP spec and created confusion. Updated all convenience methods (debug(), info(), warning(), error()) for consistency.

[Copilot]

Pull request overview

This PR aims to make context logging spec-compliant by allowing structured (JSON-serializable) log payloads (issue #397) and updates tests to validate logging of non-string values.

Changes:

• Adds a new test covering structured log data types (dict, list, number, boolean, string).
• Updates the client logging-callback test to pass structured fields via data= instead of extra=.
• Adds a new Context.log(..., data: Any) + convenience logging methods in mcpserver/server.py.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 6 comments.

File	Description
tests/server/mcpserver/test_server.py	Adds a structured-data logging test intended to validate spec compliance.
tests/client/test_logging_callback.py	Updates one logging call to use the new data= shape rather than extra=.
src/mcp/server/mcpserver/server.py	Introduces new Context/logging implementation and a StreamableHTTPASGIApp class definition.

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

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[akshay-kumar-bm]

Hi maintainers, this PR addresses #397 by making FastMCP context logging spec-compliant.

Summary of changes:

• Context.log() and helper methods now accept structured JSON-serializable payloads (Any) instead of only str.
• Removed the old extra-style pattern and aligned the logging API behavior with the MCP spec.
• Added/updated tests to validate dict/list/number/boolean/string logging and keep string logging behavior working.

@maxisbey @alejandro5042 could you please review this when you have time? Thank you!