feat(registry): carry a server's own initialize instructions on the overview

[yh928]

Summary

The MCP handshake returns instructions — free-form guidance the server wants the client to have. McpInitializeResult already parses it and both transports already cache it. Nothing read it, so it was discarded exactly where it is most useful.

This carries it onto ConnectedServerOverview.

Problem

ConnectedServerOverview is what a host renders a connected server from. For a hand-added server there is no registry entry, so description is None and the line a host can produce degrades to a name plus "N tools available" — which says nothing about what the server does.

The server's own initialize instructions are the only thing that can answer that, and the protocol already delivers them.

Change

• ConnectedServerOverview::instructions: Option<String>, #[serde(default)] so an overview written before the field existed still decodes (as None).
• Connection captures the handshake's instructions at connect time; connected_overview copies them out.

Three details worth stating, since each was a choice:

Captured once, not read per overview. The value cannot change without a reconnect, and a reconnect rebuilds the whole record anyway. connected_overview is on a prompt-rendering path, so making it await a transport per server would be the wrong trade.

The read cannot dial again. It runs after list_tools, which cannot have succeeded without a completed handshake, so initialize() returns the cached result.

A transport error yields None, the same as a server that sent nothing. The caller is describing a server; a missing description is not worth failing the listing over.

Trust

Documented on the field as untrusted remote text needing sanitization before it reaches an LLM's context — the same warning description already carries, and the same one transport/mod.rs gives for this value. This PR only carries it; it does not decide how a host renders it.

Tests

678 + 150 pass. The round-trip test covers the new field, and a new test pins that a payload written before it existed still decodes rather than failing the whole overview and taking the server listing with it. fmt clean.

cargo clippy fails on this toolchain for an unrelated pre-existing reason — #[allow(clippy::unused_async_trait_impl)] at tinymcp/src/tinybus_module/service.rs:122 is an unknown lint here. Untouched by this PR (3 files, +55 lines).

Related

Unblocks tinyhumansai/openhuman#5321, which wants to fall back to a server's instructions in the orchestrator prompt when the registry has no description for it. That change lives in openhuman; this is the one field it needs from here.

[coderabbitai]

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[tinysweeper]

How this change flows

3 changed behaviours across 9 relationships. 5 surrounding behaviours are shown (60 graph nodes walked). 42 further behaviours left out to keep the diagram readable.

flowchart LR
  n0["ActiveClient<br/>changed"]:::changed
  n1["Connection<br/>changed"]:::changed
  n2["Connections<br/>changed"]:::changed
  n3["connect_inner"]:::impacted
  n4["dial_remote"]:::impacted
  n5["all_status"]:::impacted
  n6["dial_stdio"]:::impacted
  n7["connect"]:::impacted
  n1 -->|uses| n0
  n2 -->|uses| n1
  n3 -->|uses| n1
  n3 -->|calls| n4
  n3 -->|calls| n6
  n4 -->|uses| n0
  n5 -->|uses| n1
  n6 -->|uses| n0
  n7 -->|calls| n3
  classDef changed fill:#0d4429,stroke:#238636,color:#e6edf3
  classDef impacted fill:#161b22,stroke:#6e7681,color:#c9d1d9
  classDef flagged fill:#5a1e02,stroke:#d93f0b,color:#ffffff
  classDef blocking fill:#67060c,stroke:#f85149,color:#ffffff

Loading

_{Green: changed behaviour. Grey: surrounding behaviour. Arrows name the call, use, implementation, or test relationship. Orange: has findings. Red: has a finding that blocks the merge.}

[tinysweeper]

tinysweeper found nothing blocking. Approving.

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