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

Beyond the readOnly/openWorld annotations, it discloses the actual behavior: a DNS TXT lookup followed by fetching the referenced logo and validating it against a specific SVG profile. It also states the two verification limits (no certificate validation, no DMARC check), which prevents over-reading the result. It does not describe error/timeout behavior for unreachable logos, keeping it from 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, the primary action front-loaded and the scope limits placed after. Every clause carries information; nothing is redundant with the title.

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 one-parameter read-only lookup with no output schema, the description covers what is inspected, what is validated, what is merely reported, and what is deliberately excluded. That is sufficient for an agent to call it correctly and interpret the result.

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?

With a single parameter at 100% schema description coverage, the schema already documents 'domain' with an example. The description confirms the parameter is interpreted as an apex domain whose BIMI setup is probed, but adds no format or edge-case detail (subdomains, IDN) 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 verb and resource ('Check a domain's BIMI setup') and enumerates exactly what is examined: the default._bimi TXT record, the l= logo, SVG Tiny P/S validation, and the a= certificate reference. It also explicitly distinguishes itself from check_spoofability, so an agent can separate it from 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?

It gives a clear usage boundary by stating it does not verify the certificate or the DMARC policy and routing DMARC enforcement checks to check_spoofability. It stops short of a full when-to-use framing (e.g., when to run this vs. other domain checks), but the exclusion plus named alternative covers the main ambiguity.

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