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

With no annotations, the description carries the full burden. It adds useful behavioral context: the result depends on a prior create_mailtest call and a user action (sending email). However, it does not disclose what happens if the user hasn't sent the email yet, whether the tool blocks/polls, or how errors are surfaced. This is adequate but not rich.

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 one sentence that is front-loaded with the action and object, then provides the necessary workflow context. Every word earns its place; no filler or redundancy.

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?

For a simple one-parameter fetch tool with no output schema, the description covers the essential context: what it returns, what it depends on, and when to call it. The only mild gap is unspecified behavior when the email hasn't been sent yet, but the phrase 'once the user has sent...' implicitly addresses that.

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 100%, and the single parameter 'id' is already documented as 'The test id returned by create_mailtest'. The tool description adds no additional parameter meaning beyond reinforcing that relationship. Baseline 3 applies since the schema carries the load.

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 uses a specific verb ('Fetch') with a precise resource ('score and breakdown of a mail test created with create_mailtest'). It also includes the precondition ('once the user has sent their email to the disposable address'), which clearly distinguishes this tool from siblings like check_blacklist or whois_lookup.

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 provides clear workflow context by linking the tool to create_mailtest and specifying the prerequisite user action. It doesn't explicitly exclude alternative tools, but the reference to the specific creation tool and the timing ('once the user has sent...') gives an agent enough guidance to know when to invoke this versus the sibling tools.

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