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

With no annotations supplied, the description carries the full burden and does so well: single-use semantics, a ten-minute expiry, a requirement to display the message unmodified, a 1 CRD cost charged even on rejection, the 429 exemption, and request_id in error results for support. These are exactly the operational facts an agent cannot infer from the schema.

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?

Five short sentences, front-loaded with the purpose and the step ordering, then progressively disclosing constraints, cost, and error handling. Nothing is redundant and no sentence could be dropped without losing a fact the agent needs.

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?

There is no output schema, and the description implies but never enumerates the success payload (message text, nonce, expiry field). For a six-parameter mutation-adjacent tool the behavioral coverage is strong, but the exact success response shape is left implicit.

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 each parameter is already documented, and the description adds no field-level meaning beyond the implied 'nonce' output. Baseline 3 is appropriate since the schema does the heavy lifting and the description only reinforces the signing flow.

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 ('get a single-use message for them to sign') and frames it explicitly as the first half of a two-step flow, which cleanly distinguishes it from the sibling verify_wallet_signature. An agent knows exactly what this returns without opening the schema.

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?

Explicitly sequences the call: 'Step 1 ... Then call verify_wallet_signature with the nonce and the signature their wallet produces.' It also names the escape hatch (x402_payment) via the schema and the 429 no-charge case, so the agent knows both the next step and the failure branches.

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