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NousResearch/hermes-agent

Unexpected 'tools' field in MCP sampling capabilities

Cluster 5468 · mcp. Data as of

3 open items. Fix merged in #131891 on 5 Oct 2026. Check it covers your case.

The short answer

1open issue
2open PRs
7items grouped
Known?
Yes. 7 related items grouped here, 2 issues already closed.
Fix event
A fix was merged to main in PR #131891. Check it covers your case. No release data is tracked.
Tracker
The maintainers' tracker marks this partially resolved, deciding PR #131891. That is separate from the fix event.
Still open
1 issue and 2 PRs.

Multiple reports and fixes relate to an unexpected 'tools' field being serialized into the MCP client handshake's sampling capabilities, causing strict servers to reject the connection. Proposed fixes involve making the field opt-in or removing it from the default serialization.

Open issues1

  • Issue#47963Zoho Calendar MCP Connection Fails with "Unrecognized field 'tools'" During Initialization

Open PRs2

  • PR#18209fix(mcp): make sampling tools capability opt-in
  • PR#106942fix(mcp): make sampling.tools capability opt-in via expose_client_tools

Fixes on record

Merged to main. A stamp counts the issues a fix is linked to.

  • #131891 fix(mcp): make sampling.tools capability opt-in via expose_client_tools [risk 0.30]

    merged to main

    files: cli-config.yaml.example, skills/autonomous-ai-agents/hermes-agent/references/native-mcp.md, tests/tools/test_mcp_tool.py, tools/mcp_tool_sampling.py

1 PR closed without merging

From the close comments: other 1

  • #55522 fix(mcp): remove empty SamplingToolsCapability from client handshake · other → #18209, #5468
Closed issues · 2
  • Closed#5468mcp_tool: SamplingCapability(tools=...) sub-capability rejected by strict MCP servers (Jackson FAIL_ON_UNKNOWN_PROPERTIES)
  • Closed#55469Bug: HTTP Streamable MCP connection fails because ClientCapabilities.Sampling serialized with unexpected "tools" field
How this cluster was grouped
  • Link evidence (partly structural links): some members are connected by structural evidence (shared changed files, or a closing/superseded reference); the rest are joined by an automated relevance judgement over their text.
  • Members outside that structural core may belong to a different underlying problem.
  • Pairwise link density 0.24: the share of item pairs that carry a link, counting a structural link in full and a relevance-only link at 0.36. 1.00 means every pair is linked.

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At a glance

Subsystem
mcp
Merged PRs
#131891
Closed issues
2
Attempts
1 PR closed without merging
Fix link checked
5 Oct 2026

For your agent

The same facts, typed.

cluster/5468.json
cluster/5468.md