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

With no annotations, the description carries full behavioral disclosure. It states determinism, one-shot retrieval, that it drains ONLY the pinned rendezvous relay, stops at the matching DM, and is free. It doesn't detail failure modes or permission needs, but it provides substantive behavioral context beyond 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?

The description is compact (about 4 sentences) and front-loaded with the primary action. Each sentence adds essential information: core purpose, retrieval mechanics, alternative path, and usage warning. No filler or repetition.

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?

The tool has an output schema (present), so return values are covered elsewhere. The description explains the two retrieval modes, the deterministic one-shot nature, the relay draining behavior, and the no-retry constraint. For a tool with 3 optional parameters, this is sufficiently complete.

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 0%, so the description must compensate. It meaningfully explains that sender_npub and dpop_token are used as a pair, that credential_card is an alternative requiring no dpop_token, and even gives a format hint ('ncred1...'). This adds value over the bare schema properties.

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 clearly states the tool's purpose: 'Pick up patron credentials from the Secure Courier.' It specifies the resource (patron credentials) and the action (pick up), and distinguishes itself from siblings like brain_receive_credentials by emphasizing the 'Secure Courier' channel and the two distinct retrieval modes.

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 description provides clear usage context: it explains two alternative input paths (sender_npub+dpop_token or credential_card) and explicitly warns 'Do NOT poll or retry.' While it doesn't name sibling tools as alternatives, it gives sufficient conditions for use within the tool itself.

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