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

No annotations are provided, so the description bears full responsibility for behavioral disclosure. It clearly explains the human-in-the-loop flow: sends a welcome DM, recipient must fill and reply manually, and warns that 'receive_credentials' destructively drains the relay mailbox. It also notes that the flow requires waiting for user confirmation. While it doesn't mention rate limits or auth requirements, it covers the most critical behavioral traits for this type of tool.

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 structured logically: core purpose, usage differentiation, flow explanation, and post-call actions. It is front-loaded with the main verb phrase and every sentence contributes meaning. It is slightly verbose with redundant emphasis (e.g., '**This is a human-in-the-loop flow.**'), but remains efficient and well-organized for the amount of critical information conveyed.

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 that an output schema exists (so return values are covered elsewhere), the description is remarkably complete. It explains the credential-delivery flow, the human-in-the-loop nature, the need to check service_status for OAuth2 services, and the correct sequencing with 'receive_credentials'. It also warns about the destructive behavior of the follow-up call. No significant gaps remain.

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 input schema has 100% coverage with descriptions for both 'service' and 'sender_npub', so the baseline is 3. The description adds minimal extra param semantics beyond the schema, though it does hint at the service parameter's origin ('e.g., from get_operator_onboarding_status or get_patron_onboarding_status') in the schema itself. The description doesn't introduce new parameter details, so a 3 is appropriate.

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+resource: 'Open a Secure Courier channel for credential delivery.' It clearly states this is for handing over service secrets like API keys and tokens, and explicitly distinguishes it from the sibling tool 'request_npub_proof' for merely proving npub control. This fully clarifies its unique purpose.

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?

Provides explicit when-to-use guidance: use it to deliver service secrets, use 'request_npub_proof' instead for npub control, and check 'service_status' first for dynamic/OAuth2 services (e.g., Schwab). Also gives detailed post-call instructions: STOP, tell the user, wait for confirmation, and do NOT poll or retry. This is exemplary usage guidance with clear alternatives and exclusions.

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