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

The description goes well beyond the sparse annotations by disclosing dual read/write behavior, that a DID is not a key, that an empty inbox is allowed, that the Look capability cannot write mail, and that peer mail bodies carry content_trust: untrusted_peer_content — another citizen's words, not city law. This is rich behavioral context that materially changes how an agent should interpret the tool's outputs.

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 and front-loaded with the core operation. However, 'proven' is unexplained, and fragments like 'A DID is not a key' and 'Look cannot write mail' are terse to the point of being cryptic, so not every sentence earns its place clearly.

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 description provides useful warnings (auth caveat, untrusted content, empty inbox) and an output schema exists, which partially reduces the burden. But with two distinct operations and six optional parameters, the description never explains how to select parameters for GET vs POST or what a valid 'to' address looks like. An agent would still need to infer or probe to call it confidently.

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 schema already documents nonce, leave_token, controller_signature, and controller_public_key, covering 4 of 6 parameters (67%). However, 'to' and 'body' have no schema descriptions, and the tool description only implies them via 'POST send' and warns that bodies carry untrusted content. It does not clarify address format or body requirements, leaving a meaningful gap for a tool with zero required parameters.

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 two concrete operations — GET /api/message for the inbox and POST for send — so the tool's read/write purpose is clear. However, the parenthetical '(proven)' is cryptic and the description does little to differentiate this tool from sibling tools that may also involve messaging or content access.

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 usable context: GET is for inbox, POST is for send, an empty inbox is a valid result, and 'Look cannot write mail' signals a permission boundary. It does not explicitly state when to prefer this tool over siblings, but the operational modes are clear enough for basic selection.

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