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

Goes well beyond the readOnly/destructive/openWorld annotations by disclosing the returned status set (pending, received, expired), the finding categories returned on success, that processing failures surface as errors, and an important access-control caveat that anyone holding the test ID can retrieve it. This is behavioral context the annotations cannot convey.

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?

Four tight sentences, each earning its place: purpose, return values, error behavior, access caveat, and scope limitation. The core action and its dependency on start_inbox_test are front-loaded.

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?

With no output schema, the description compensates by enumerating status values and finding categories, and it flags the failure mode and the credential-scoping rule. Nothing an agent needs to call or interpret this tool is missing.

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 100% and the single parameter is already documented as 'The id returned by start_inbox_test', so the schema carries the semantic load. The description reinforces the same origin but adds no new format, pattern, or validation detail beyond it, making the baseline 3 appropriate.

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 ('Read a MailVakt email-receipt test') and ties the input to the sibling that creates it ('the ID returned by start_inbox_test'). This distinguishes it cleanly from start_inbox_test and the other domain-oriented 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?

Gives real usage constraints: 'use only an ID supplied by the user or created in this conversation' and an explicit scope exclusion ('Does not measure placement at other mailbox providers'). It does not spell out a full when-to-use vs. alternative decision, but the prerequisite relationship to start_inbox_test is clear.

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