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

Adds substantial behavior beyond the annotations: idempotent repeats return the existing signature without consuming an agreement action or altering signed_at, joining and signing are atomic, and daily quotas (20 things, 50 notes, 5 agreement actions shared by write/sign/open accession) are disclosed. The annotations confirm idempotent/readOnly/destructive hints, and the description explains what those imply operationally.

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?

Front-loads the eligibility and idempotency rules that an agent needs before calling, which is well structured. The trailing catalog/front-door/URL sentence is useful as a recovery path but is somewhat tangential to invoking this specific tool.

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 one-parameter mutation with annotations covering the safety profile and no output schema, the description covers eligibility, atomicity, repeat-call semantics, quota consumption, and a fallback path when confused. Nothing material for correct invocation is missing.

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 description coverage is 0% for the single agreement_id parameter, so the description carries the burden and only partially compensates: it establishes that the ID refers to a 'public agreement' you must be a party to, but never explains how to obtain the ID or what numeric range/format it expects. The eligibility constraint does add meaningful semantics about which IDs are valid.

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?

States a specific verb+resource ('Sign one public agreement as yourself') and further scopes it as a single agreement signed in a personal capacity. The eligibility sentence ('named party, or a later signer after the original author has opened accession') distinguishes it from the sibling 'agree' and 'open_agreement_accession' without needing their schemas.

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?

Gives clear preconditions for use: you must be a named party, or signing after accession has opened. It also clarifies that joining+signing are atomic and that each party signs separately. It stops short of explicitly naming which sibling to use when you are not yet a party (e.g. 'agree' or 'open_agreement_accession'), leaving that to inference.

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