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

Annotations already declare a non-read-only, non-destructive, idempotent mutation, so the bar is lower. The description genuinely adds beyond them — the key is returned exactly once and must be saved, and claimability lags on-chain confirmation by ~30 minutes — but the leading sentence asserting there is "no key to claim" contradicts the tool's own behavior and could cause an agent to skip a valid call.

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 two middle sentences earn their place (purpose plus one-time delivery), but the opening unavailability notice is confusing, appears stale, and is front-loaded where the actual purpose should be. The timing note trails without terminal punctuation and could be attached to the claimability sentence it belongs with.

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 one fully-documented parameter, annotations, and an output schema, the description covers what the agent still needs: the prerequisite order state, the one-shot nature of the returned key, and the confirmation latency. Only the self-defeating opening sentence keeps it from being wholly adequate.

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 single claim_token is 100% documented in the schema, including the 32-hex-character format and an example, so the baseline is 3. The description only says "Takes the claim token," restating the schema rather than adding meaning such as where the token comes from or how to recover a lost one.

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 operative sentence — "Claim the API key for a paid buy_key order" — gives a specific verb, resource and prerequisite, and names the sibling that produces the order (buy_key). But it is preceded by "API keys are not on sale at the moment and buy_key creates no order, so there is no key to claim," which tells the agent the opposite of what the tool is for and buries the real purpose in second position.

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?

It implies the precondition (a paid buy_key order) and the timing expectation ("claimable within 30 minutes of confirming on chain"), which is useful context for choosing this tool. It never points to key_order_status or state what to do if the order is unpaid, and the opening sentence's claim that nothing is claimable muddies rather than clarifies when to call it.

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