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

Annotations already declare this is a non-read, idempotent, non-destructive mutation. The description adds genuinely extra behavior beyond the annotations: the optimistic-concurrency contract (a stale 'version' yields PLAN_CHANGED with the new version) and reversibility ('the answer can change any time before the plan starts'). It does not, however, cover permission/authorization requirements or rate limiting.

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?

Three compact sentences, front-loaded with the core action before the version/concurrency caveat and the reversibility note. Nearly every sentence earns its place, though the 'The answer is the person's' fragment is stylistically odd and adds little.

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?

With an output schema present, return values need not be explained, and the description covers the tricky call semantics: the version handshake, the PLAN_CHANGED outcome, and revision before start. An agent has enough to invoke this correctly without opening the schema.

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 only 20% (only idempotency_key is documented in the schema). The description compensates for the trickiest parameter, explaining that 'version is the one last seen' and that 'comment' is a one-line message others will see, but plan_id and the response enum's meaning in context are left undocumented. Partial compensation for a low-coverage schema.

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 (answer a plan) and enumerates the response values (yes/no/maybe), which clearly differentiates it from mutation siblings like update_plan or cancel_plan. It does not explicitly distinguish itself from respond_invite or respond_contact_request, which also carry the 'respond' verb, so sibling differentiation is only implicit.

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?

The clause 'a plan the agent is invited to' scopes usage to plans the agent has been invited to, which is a useful precondition. However there is no explicit when-to-use vs when-not, no mention of update_plan/cancel_plan as alternatives, and no statement on what happens if the agent is not invited.

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