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

With no annotations at all, the description carries the full burden and does well: it discloses the return payload (token and seed addresses), that notification emails default to off, that the operation is non-idempotent and must not be auto-replayed, and an input precondition that isn't obvious from the schema.

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?

Telegraphic but front-loaded and waste-free: purpose first, then prerequisites, return shape, workflow, defaults, and the safety caveat. Every sentence adds a distinct fact.

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 the workflow and partially the return shape with no output schema to lean on, but for a 6-parameter tool with zero schema descriptions, the optional parameters (providers, locale, report flags) have no meaning anywhere. The description does not explain what is polled or what the token is used for.

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 description coverage is 0% across 6 parameters, so the description must compensate. It clarifies the required email semantically (sender address, not the login email) and hints that notification-type flags default off, but providers, emailLocale (the only enum), senderLinkReports, and finalReportEnabled are never explained.

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 and resource ("Create one free inbox-placement test") plus a scope constraint (single, free test). The create action naturally separates it from the get and list siblings without needing to name them.

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 a real workflow: create, send the actual message to the seed addresses, then poll for measured results, and warns against automatic replay of the POST. It also excludes a plausible wrong input ("not email-login"). It stops short of naming guest_tests_get as the polling tool or stating when to prefer alternatives.

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