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

The confirm-gated preview behavior and the coach-only restriction on loggedAt are genuinely useful, but the confirm semantics are already spelled out in the schema's confirm parameter description, so the marginal disclosure is limited. It says nothing about whether the message notifies the client, whether logs can later be edited or removed, or what the preview response contains.

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 tight sentences, front-loaded with the core action and followed by the coach-on-behalf case, the bulk alternative, and the confirm gating. The parenthetical confirm note partially repeats the schema's confirm description, which is the only redundancy.

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 nested-parameter mutation with no output schema and only readOnlyHint=false in annotations, the description covers the gating model, the backdating semantics, and the bulk alternative. Return shape is not needed, though the absence of any error or permission context keeps it from being fully complete.

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?

With only 50% schema coverage and a nested input object, the description earns its keep by explaining answers (questionId sourced from get_checkin) and loggedAt (past ISO date/time so it shows when it really happened). checkInId and value remain undocumented anywhere, which is a minor gap since the former is self-evident.

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 and resource (add a coach message plus optional answers to a check-in) and explicitly separates itself from import_checkin_history for bulk back-filling. It does not differentiate from the other check-in-answering sibling, respond_to_checkin, so an agent still has to infer the coach-on-behalf distinction.

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 a concrete when-to-use: a coach entering answers on the client's behalf, and backdating via loggedAt for history. It also routes bulk past entries to import_checkin_history. It never states when not to use it (e.g. vs respond_to_checkin for the client's own answers).

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