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

Annotations declare the safety profile (readOnly=false, destructive=false, idempotent=false, openWorld=false), and the description adds genuinely operational context beyond them: the api_key is returned only once, it must be retained, and it is consumed by later calls as a Bearer token. That once-only credential disclosure is exactly the kind of behavioral trait annotations cannot express.

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?

Three short sentences, front-loaded with the action and the returned artifacts, then the negative scope, then the credential-handling requirement. Every clause carries non-redundant 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 present, the description carries the return-value burden itself and does so by naming wallet_id, api_key, and balance_credits, plus how the api_key is subsequently used. Nothing essential for correct invocation 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 description coverage is 100% and the single optional 'label' parameter is fully documented in the schema, including its 1-80 character bound and its equivalence to POST /v1/wallets. The description adds no parameter-level detail, 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?

States a specific verb and resource ("Create a wallet") plus the exact return payload (wallet_id, api_key, balance_credits 0). It also negates a nearby misconception with "This does not look up an existing wallet," so an agent can tell it apart from any retrieval-style call and from siblings like get_balance or create_checkout.

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 explicit when-not guidance ("does not look up an existing wallet") and forward-looking usage ("later tools need it as Authorization: Bearer or as api_key"). It stops short of naming a concrete alternative sibling for wallet lookup, but no such sibling exists in the listed set, so the guidance is contextually sufficient.

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