Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnly, idempotent, non-destructive and openWorld, so the safety profile is covered. The description adds genuinely new behavioral context beyond that: the response is an ES256-signed JWS and how to validate its signature against a public key endpoint, plus the auth requirement.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two tightly packed sentences with no filler, and the artifact being returned is front-loaded ahead of the verification instruction. Dense but efficient.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a read-only, idempotent retrieval with no output schema, the description covers what is returned, how to trust it, and the auth need. It does not mention failure cases (e.g., a match with no mutual consent yet), which is a minor gap for a 2-parameter tool.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so both match_id and api_key are already documented, which sets the baseline at 3. The description adds the provenance of api_key (register_agent), but its phrasing 'Needs your api_key' is in mild tension with the schema's 'Optional: only if your MCP client cannot send an Authorization header.'

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description concretely characterizes the returned artifact as an 'ES256-signed JWS proving the mutual match,' which tells an agent this retrieves cryptographic proof of a match rather than, say, handoff data or stats. It is clear on resource and output, though it never explicitly contrasts itself with siblings like get_handoff or list_matches.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It supplies a prerequisite ('Needs your api_key (from register_agent)') and post-retrieval guidance ('verify with /.well-known/peerlace-keys.json'), which is more than bare implied usage. However it never states when to prefer this over the other match-related siblings, so alternative selection is left to inference.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.