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

With no annotations, the description carries the full behavioral burden, and it delivers: deterministic one-shot retrieval, draining only the pinned rendezvous relay, deletion/NACK of wrong DMs, stopping at the first matching DM, courier_not_found on no match, and payment processor client reinitialization on success. No annotation contradiction exists.

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?

Although longer than average, each sentence earns its place: action, flow context, call precondition, drain semantics, alternative path, and side effect. It is well-structured and front-loaded with the core purpose before diving into protocol details.

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?

Given the complexity of a deterministic one-shot credential retrieval and the absence of annotations, the description is complete. It covers call timing, relay draining behavior, failure semantics, the credential_card bypass, and the post-success reinitialization. Since an output schema exists, not detailing return shape is acceptable.

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% and each parameter already has a description, so the baseline is 3. The tool description adds relational meaning beyond the schema: service must match request_credential_channel, dpop_token is the session phrase for this exact channel, sender_npub identifies the credential sender, and credential_card bypasses relay access entirely.

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 description opens with a specific verb and resource: 'Pick up credentials from the Secure Courier.' It names the CREDENTIAL-DELIVERY flow and explicitly distinguishes its counterpart receive_npub_proof, making the tool's role clear relative to siblings such as receive_patron_credentials and forget_credentials.

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 gives an explicit precondition: 'Call this only after the user confirms they have replied.' It also tells the agent what not to do: 'Do NOT poll, loop, or retry.' The credential_card alternative path is explained with the condition under which dpop_token is not needed.

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