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

Beyond the annotations, the description discloses important behavior: it returns private credentials, existing credentials rename the same participant, and it does not verify identity or grant organizer rights. Those are exactly the side effects and security limitations an agent needs before invoking a mutation tool with destructiveHint=true and openWorldHint=true.

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?

The action is front-loaded in the first sentence, followed by usage guidance, the rename nuance, and the identity/organizer limitation. The four sentences are tight and each carries distinct information without repetition.

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 six-parameter mutation tool with full schema coverage and annotations but no output schema, the description covers the essential behavioral context: what it does, when to use it, that it returns private credentials, the rename behavior with existing credentials, and the lack of identity verification or organizer rights. Nothing an agent needs in order to call it correctly 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 100%, so the schema already documents plan, name, selection, participant_id, participant_token, and existing_participant_id thoroughly. The description adds the useful nuance that existing credentials rename the participant, but it does not explain the selection enum or the distinction between participant_id and existing_participant_id, so it stays at the baseline for a fully documented 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?

The description states a specific verb and resource: it adds the user to a saved plan or selects an existing participant by name, and returns that person's private credentials. It also clarifies that existing credentials cause a rename rather than a new add, which distinguishes this action from create_plan and get_plan without relying on the schema.

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 explicitly says to use this when the user wants to take part in an existing plan or act as a specific participant. That is clear usage context, but it does not name alternatives such as create_plan for missing plans or get_plan for read-only inspection, and it gives no explicit when-not guidance beyond the identity/organizer limitation.

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