check_bimi

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

Beyond the readOnly/idempotent/non-destructive annotations, the description explains what is actually validated, the limitation that the certificate type is not determined from the bare a= tag, the DMARC enforcement prerequisite, and that findings cover missing/malformed records or unmet prerequisites. This adds meaningful behavioral context without contradicting annotations.

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 three sentences, starts with the core action and target, and every clause adds value: validation logic, limitation, prerequisite, returned findings, and use case. No filler or repetition.

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?

Given the annotations describe safety, the schema fully documents parameters, and an output schema exists, the description provides sufficient behavioral detail: exact record, fields validated, limitation, prerequisite, and outcome types. Nothing critical is missing for an agent to select and invoke this tool correctly.

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%, so the schema already documents domain, format, and force_refresh. The description adds domain semantics by specifying the lookup at default._bimi.<domain>, but it does not add further detail on format or force_refresh beyond the schema.

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 names a specific resource (default._bimi.<domain>), a precise action (check/validate), and the exact fields validated (l= and a=), while also verifying the DMARC prerequisite. This clearly distinguishes it from the many other DNS/record checking siblings like check_dmarc or check_tlsrpt.

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 explicitly says to use it 'to assess brand-indicator readiness in inboxes' and notes it is 'part of the scan_domain audit,' providing clear context. It does not name alternatives or state when not to use it, but the use case is unambiguous enough.

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