Surface MCP tool-result _meta to the model, minus protocol-reserved keys (port from kimi-code) - #80712
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૮ >ﻌ< ა ci reviewran on bba748f — Port from MoonshotAI/kimi-code#2596/#2600: surface MCP tool-
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…eta to the model, minus protocol-reserved keys MCP tool results carry a server _meta mapping (exposed as .meta by the Python SDK) alongside structuredContent. Servers return namespaced machine-readable contracts there (validated payloads, browser-handoff URLs); Hermes previously dropped the field entirely, so that data was invisible to the agent. Now _meta is included in the JSON tool output, after filtering protocol-reserved keys per the MCP spec's key-name rules: a prefix is reserved when a modelcontextprotocol or mcp label is followed by at least one more label (modelcontextprotocol.io/..., tools.mcp.com/...). Vendor namespaces with a trailing reserved word (com.example.mcp/...) and unprefixed keys pass through. Non-serializable metadata drops the extras rather than failing the call.
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…scout-slate wave Post-merge docs sweep for the Aug 16 scout slate. Two pages: - mcp.md: tool-result sanitization section — invisible Unicode TAG chars (U+E0000-E007F) stripped from results/resources/descriptions (#80689); vendor _meta surfaced to the model minus protocol-reserved modelcontextprotocol/mcp prefixes (#80712) - tools.md: tool result annotations section — signal-death exit notes (subprocess -signum definite, shell 128+signum hedged) (#78074); UTF-16 read_file transcoding with disclosure hint and 10MB cap (#80717) Security-policy docs (approvals/allowlist) intentionally untouched.
teknium1
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…scout-slate wave Post-merge docs sweep for the Aug 16 scout slate. Two pages: - mcp.md: tool-result sanitization section — invisible Unicode TAG chars (U+E0000-E007F) stripped from results/resources/descriptions (#80689); vendor _meta surfaced to the model minus protocol-reserved modelcontextprotocol/mcp prefixes (#80712) - tools.md: tool result annotations section — signal-death exit notes (subprocess -signum definite, shell 128+signum hedged) (#78074); UTF-16 read_file transcoding with disclosure hint and 10MB cap (#80717) Security-policy docs (approvals/allowlist) intentionally untouched.
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…scout-slate wave Post-merge docs sweep for the Aug 16 scout slate. Two pages: - mcp.md: tool-result sanitization section — invisible Unicode TAG chars (U+E0000-E007F) stripped from results/resources/descriptions (NousResearch#80689); vendor _meta surfaced to the model minus protocol-reserved modelcontextprotocol/mcp prefixes (NousResearch#80712) - tools.md: tool result annotations section — signal-death exit notes (subprocess -signum definite, shell 128+signum hedged) (NousResearch#78074); UTF-16 read_file transcoding with disclosure hint and 10MB cap (NousResearch#80717) Security-policy docs (approvals/allowlist) intentionally untouched.
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…scout-slate wave Post-merge docs sweep for the Aug 16 scout slate. Two pages: - mcp.md: tool-result sanitization section — invisible Unicode TAG chars (U+E0000-E007F) stripped from results/resources/descriptions (NousResearch#80689); vendor _meta surfaced to the model minus protocol-reserved modelcontextprotocol/mcp prefixes (NousResearch#80712) - tools.md: tool result annotations section — signal-death exit notes (subprocess -signum definite, shell 128+signum hedged) (NousResearch#78074); UTF-16 read_file transcoding with disclosure hint and 10MB cap (NousResearch#80717) Security-policy docs (approvals/allowlist) intentionally untouched.
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…scout-slate wave Post-merge docs sweep for the Aug 16 scout slate. Two pages: - mcp.md: tool-result sanitization section — invisible Unicode TAG chars (U+E0000-E007F) stripped from results/resources/descriptions (NousResearch#80689); vendor _meta surfaced to the model minus protocol-reserved modelcontextprotocol/mcp prefixes (NousResearch#80712) - tools.md: tool result annotations section — signal-death exit notes (subprocess -signum definite, shell 128+signum hedged) (NousResearch#78074); UTF-16 read_file transcoding with disclosure hint and 10MB cap (NousResearch#80717) Security-policy docs (approvals/allowlist) intentionally untouched.
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Summary
MCP tool results now surface the server
_metamapping to the model, with protocol-reserved keys filtered out. Previously the field was dropped entirely, so servers returning namespaced machine-readable contracts (validated payloads, browser-handoff URLs) in_metawere invisible to the agent.Ported from MoonshotAI/kimi-code#2596 + #2600 (their
<mcp-structured-result>block), adapted to Hermes' existing JSON tool-output shape intools/mcp_tool.py.Changes
tools/mcp_tool.py:_make_tool_handlerresult assembly includes_meta(SDK exposes wire_metaas.meta); new_is_reserved_mcp_meta_key()/_strip_reserved_meta_keys()helpers implement the MCP spec key-name rules — a prefix is reserved when amodelcontextprotocolormcplabel is followed by at least one more label (modelcontextprotocol.io/...,tools.mcp.com/...); vendor namespaces with a trailing reserved word (com.example.mcp/...) and unprefixed keys pass through. Non-serializable metadata drops the extras rather than failing the call.tests/tools/test_mcp_structured_content.py: 8 new tests (passthrough, reserved-key filtering, all-reserved omission, combination with structuredContent, non-serializable, non-dict, predicate unit tests).Validation
_metain tool outputCallToolResult.model_validate({..., "_meta": {...}})→.metapresent, filter verifiedInfographic