claim_username

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

With no annotations, the description carries the full behavioral burden. It discloses the authentication prerequisite and that the username is unique, but it does not explain failure behavior for an already-taken username, whether claiming replaces an existing username, or what the response indicates. This is partially transparent but leaves important edge-case behavior implicit.

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 description is short and front-loaded with the core action, plus a separate ACCESS note for authentication. It loses a point because the username validation rule is duplicated from the schema, but the overall structure is clean and scannable.

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 tool with no output schema, the description provides the essential context: what is claimed, for whom, the constraints, and how to authenticate. It lacks explicit error/return-value details, but the agent has enough information to invoke the tool 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?

The input schema covers the username parameter completely with type, pattern, min/max length, and a description. The tool description essentially repeats these constraints rather than adding new semantic meaning, so the baseline of 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?

The description opens with a specific verb-resource pair: 'Claim a unique username for the authenticated user's public profile.' This clearly states the action, the object, and the scope, distinguishing it from the large sibling set. The uniqueness and character constraints add useful precision.

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 description provides clear context for when the tool is usable: the user must have a Proof account, and the agent must either set PROOF_API_KEY or complete sign-in via start_login before calling. It does not explicitly name alternatives, but none of the siblings directly compete with this action.

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