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

With no annotations provided, the description carries the full behavioral burden and does so: it discloses the welcome DM with a credential template, that the flow is human-in-the-loop requiring manual reply, and the critical destructive trait that each receive_credentials call drains the relay mailbox. This is unusually rich disclosure for a mutation-adjacent flow.

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?

Front-loads purpose, then differentiation, then the operational flow and warnings. Every sentence earns its place — the when-not guidance and the do-not-poll instruction are all actionable, with no filler.

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?

An output schema exists, so return values need not be explained. For a human-in-the-loop tool with no annotations, the description covers prerequisites (check service_status), the required stopping point, and the sequencing to receive_credentials — everything an agent needs to invoke it correctly.

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% for both parameters, so the schema already documents 'service' and 'sender_npub' including their sources. The description adds no syntax or format detail beyond what the schema provides, so the baseline 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 ('Open a Secure Courier channel for credential delivery') and immediately scopes it as the CREDENTIAL-DELIVERY flow, distinguishing it from sibling flows. An agent can tell it apart from request_npub_proof and receive_credentials without opening any 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 names the condition that selects this tool (handing over a service secret like API keys/tokens) and the alternatives for other cases: request_npub_proof for npub proofs and service_status for dynamic/OAuth2 services that need no couriered secret. It also gives a sequencing rule — stop after calling, wait for user confirmation, do not poll.

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