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

Annotations declare a non-read-only, non-destructive, non-idempotent mutation, and the description adds substantial context beyond them: a rate limit of 3 renames per rental, explicit non-effects (time left, escrow, and billing are unchanged), immutability of past match records, receipts, and ledger rows, and the registered-key requirement. What it does not state is what the response returns on success versus on a rejected rename (e.g., rate-limit or mid-match error), leaving a small gap.

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 WHEN clause is front-loaded and most sentences carry operational weight: preconditions, rate limit, side-effect boundaries, and an example call. The 'VIP perk from Nov 16' parenthetical adds a date and policy trivia that is marginally useful and slightly interrupts the core guidance, keeping it just short of fully tight.

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 3-parameter mutation with no output schema, the definition covers who may call it, when it is legal, what it changes, what it explicitly does not change, limits on repetition, key requirements, and a concrete invocation example. An agent has everything needed to decide and call correctly.

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 hire_id, nickname, and key are already documented, including the 1-24 char nickname limit. The description adds the example invocation and the nickname policy (reserved names, no impersonating a real handle, no city-pa/system), which is genuinely beyond the schema, but it does not explain hire_id sourcing beyond what the schema's 'Rental id from rent_hire / rent_status' already conveys, keeping this near the baseline.

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 target: change the public nickname on the RENTED tag for an existing rental. It explicitly scopes the object (the rented tag, not the bot itself) and references the sibling rent_hire only for shared nickname rules, so an agent can distinguish it from rent_hire or rent_status without reading 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?

A dedicated WHEN clause names the precondition (you already have an active rental) and the intent (change the public nickname). It adds explicit exclusions and constraints: only the renter, only while active, only between matches, with the VIP/House Bot exception spelled out, so the agent knows both when to call and when not to.

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