claim_username

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

Annotations declare readOnlyHint=false and destructiveHint=false, so the safety profile is partly covered. The description adds meaningful context: the username must be unique, its format constraints, and the auth requirement. It stops short of saying whether the username can later be changed or what failure looks like on collision.

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?

Two tight paragraphs, front-loaded with the action, then constraints, then access requirements. No filler, though the constraint sentence slightly duplicates the schema.

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 single-parameter mutation with no output schema and minimal annotations, the description covers what it does, its constraint, and the auth precondition. It omits post-success behavior (return value, mutability of the username), a minor gap.

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 single parameter is already fully documented with pattern and length bounds. The description restates the same 3-30 / alphanumeric-underscore rule, adding no meaning beyond the schema, so the baseline 3 applies.

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 (claim) and resource (username) with scope (authenticated user's public profile), plus uniqueness. Clear enough that an agent distinguishes it from profile/email/phone mutation siblings at a glance.

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 ACCESS block gives clear precondition context: a Proof account is required and the agent should either set PROOF_API_KEY or sign in via start_login before calling. It doesn't name exclusions, but there is no direct alternative tool, so routing guidance is largely moot.

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