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

Description discloses strong behavioral traits beyond annotations: pricing ($0.01 per inbox-week, $0.15 per call x402), capacity limits (500 messages, 5 MB each), and lifecycle actions (list/read/delete). Annotations only cover readOnly/openWorld, so this adds real value. However, readOnlyHint=true conflicts semantically with create/delete/extend actions — flagging as potential annotation mismatch but not a hard contradiction since reads are the primary mode. No output format described.

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?

Two sentences, front-loaded with the value proposition (email address + API read), followed by pricing and capacity. No filler, though the pricing string is dense and could be structured more 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?

Covers what the tool does, cost, and capacity – useful for a paid, mutating resource. But with 7 params at 29% schema coverage, no output schema, and no guidance on when to use vs siblings, an agent lacks enough to confidently invoke the correct action or interpret params.

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 coverage is only 29% – most of the 7 parameters (id, since, token, weeks, address) are undocumented in the schema, and the description provides no parameter-level explanation. It mentions actions (create/list/read/delete/extend) which maps to the 'action' enum but doesn't explain id vs name vs address or the meaning of since/weeks/token. Description fails to compensate for the low coverage.

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 resource ('real email inboxes for agents') and the concrete capability (receives mail, read it through the API), with a sample address format. It doesn't name or contrast with siblings like inbox, mailbox, email_send, or email_analyze, so routing unsure, but the purpose itself is unmistakable.

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?

No explicit when-to-use guidance and no contrast with the many sibling email tools (inbox, mailbox, email_send, email_analyze). Listing of use cases (sign-up confirmations, replies, receipts) gives implied usage but no condition that selects this tool over alternatives.

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