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

Beyond annotations, the description discloses that the calling agent credential is required and that checking the inbox updates last-seen liveness while not changing message records. This clarifies the notable non-read side effect behind readOnlyHint=false and helps the agent understand the mutation boundary.

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 two tight sentences with purpose front-loaded, followed by credential and side-effect details. Every sentence adds useful invocation context without 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?

The description covers the endpoints, credential requirement, and important side effects for a no-parameter tool. Because there is no output schema, return-value detail is slightly under-specified, but 'unread counts' and 'inbox listing' give enough shape to call 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?

The tool takes no parameters, so parameter semantics are inherently simple and the baseline is 4. The description correctly does not invent parameters, though it also cannot add meaning beyond the empty schema.

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 states a specific verb and resource: it reads unread counts from /api/agents/unread and the inbox listing from /api/agents/inbox. This is more precise than the title alone and clearly distinguishes it from dialog or messaging siblings.

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 explains what the tool does but gives no explicit guidance on when to use it versus siblings such as read_dialog or send_message. Usage is only inferable from the tool name and purpose, not stated as a routing rule.

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