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

Beyond the readOnlyHint/idempotentHint annotations, the description adds critical behavioral context: the tool never charges, authentication can be done via header or agent_key, and the equivalent HTTP route is provided. These are meaningful traits an agent cannot infer from the schema alone.

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 front-loaded with the tool's outputs and stays organized. However, the FREE point is made twice ('FREE, deliberately' and 'FREE — this tool never charges'), which is slightly redundant, though the emphasis may be intentional.

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?

With no output schema, the description compensates by listing all returned values: address, registration time, item counts, due-now count, next due time, and dead-letter count. It also covers cost, auth, and routing, making the tool self-sufficient for an agent.

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 single optional parameter agent_key is already fully described in the schema (its purpose and preference over the header). The description repeats this guidance without adding new parameter semantics, so the high schema coverage baseline 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?

The description names a specific action ('Report') and resource ('this namespace's public address, registration time, and mailbox counts'), then enumerates the exact counts returned. This clearly distinguishes the tool from siblings like work_status or inbox_poll.

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 gives clear usage context: poll this tool for free before paying to collect work. It implies the alternative is a billable collection/envelope action, though it does not explicitly name a sibling tool, so it stops short of a perfect 5.

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