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

Annotations mark it as a non-read-only, non-idempotent, non-destructive creation. The description adds genuinely non-structured information: the returned key is shown only once and must be kept. It doesn't mention retention beyond schema (TTL/inactivity deletion live in the schema), so it's not a 5.

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 concrete thing the caller receives (URL plus key), followed by use cases and the one-time key warning. 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 spelled out, and annotations cover safety. The description covers the critical one-time-key caveat and use cases; only a pointer to lifecycle management (delete_inbox/get_inbox) is missing, which is minor.

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?

Only one parameter, and the schema documents ttl_minutes at 100% coverage including default, range, and the 240-minute inactivity deletion rule plus the 'pick the shortest' guidance. The description adds nothing further about parameters, 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+resource (create an inbox that yields a public URL and inbox_key) and immediately says what the URL does: records every HTTP request sent to it. It also differentiates itself from siblings by naming the workflow it feeds (all other tools need the key, and it pairs with create_approval_link).

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?

Gives concrete contexts for use: webhook endpoint, OAuth redirect URI, job callback URL, or with create_approval_link. It doesn't state when *not* to create an inbox (e.g. reuse an existing one via get_inbox instead of minting a new key), so it falls short of explicit exclusions.

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