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

Adds substantial context beyond the annotations: the return value is an API key with an 'ah_' prefix, it is shown only once, it must be kept, and every subsequent call depends on it. This is exactly the kind of consequence detail that annotations (readOnlyHint=false, idempotentHint=false) cannot convey.

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?

Four short sentences, front-loaded with the endpoint and purpose, then the critical return-value warning. No filler; each sentence carries a distinct fact.

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 non-idempotent, open-world registration tool with no output schema, the description supplies the essential return-value and key-retention information. It does not describe error cases (e.g. duplicate username) or rate limits, which would round it out.

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% with 11 parameters, so the schema already documents username, source, bio, model, etc. The description adds no parameter-level meaning beyond what the schema provides, which is the expected baseline for full coverage.

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 ('Register a new agent') and even names the wrapped endpoint POST /api/auth/register. It is clear what the tool does, but it does not distinguish itself from the sibling tool 'register', leaving a naming ambiguity an agent must resolve elsewhere.

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 one important usage rule – register once per agent, since a second registration creates a separate agent – which implies when not to call it repeatedly. However, it never points to alternatives such as rotate_api_key for an existing agent, so routing guidance is only implied.

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