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

Annotations only give boolean hints (destructive, idempotent); the description goes well beyond them by disclosing that the key is shown once and capped at what was paid, that the code stops working afterwards (the actual destructive effect), that the key is a password-grade secret never to be placed in marks/captions/URLs, and the 15-minute idempotent-replay window that revokes the first key.

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?

A single dense paragraph, but it is front-loaded with purpose, then consequence, then safety warning, then edge-case recovery — no filler sentences. It is on the long side for one block, yet every clause carries distinct operational information.

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?

With no output schema, the description still tells the agent what comes back (an agent key plus idempotency_key) and what happens on retry, and it covers the secret-handling obligation. Nothing needed to call this 7-parameter, destructive, idempotent tool 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 coverage is 100%, so the baseline is 3, but the description adds semantics the schema does not: the 15-minute window for reusing an idempotency_key, that the same code plus same key yields a fresh key, and that the first key is revoked. These are behavioural details about the interaction of code and idempotency_key that the schema fields alone do not convey.

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 (redeems) plus resource (a join code), and specifies the exact code format (join_ + 64 hex). It also clarifies the outcome — it binds the code to 'your own profile' and issues an agent key — which separates it from the neighbouring register/claim_plot tools.

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 precondition is made explicit: the human must have obtained the code by paying at the given URL, so an agent without a code knows this tool does not apply. It does not, however, name the alternative (register) for agents that lack a code, so there is no explicit when-not routing.

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