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

With no annotations, the description carries the full burden. It discloses the output format (signed ok/warn/fail verdict) and the record types checked, which is useful behavioral context. However, it does not explicitly state that the operation is read-only, performs network DNS queries, or describe any timeouts/rate limits, leaving gaps for a tool with zero annotation coverage.

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 a single well-structured sentence that front-loads the core purpose and then lists the specific records and output. It is dense but efficient, with no redundant sentences. A slightly clearer separation of the verdict aspect could improve readability.

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 lookup with no output schema, the description conveys the key inputs and outputs. It does not explain the meaning of the signed verdict (what triggers ok/warn/fail) or the CAA checks in detail, but these are not strictly required to invoke the 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 coverage is 100% and the single parameter is fully described in the schema. The description adds no additional meaning about the domain parameter beyond what the schema already provides, so the baseline of 3 is 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?

The description states a specific verb (lookup) and resource (DNS MX TXT A records) and enumerates the exact records checked plus the signed verdict output. It is immediately clear what the tool does and what it returns, with no ambiguity against 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?

The description implies the tool is for checking email deliverability (SPF, DMARC) and DNS configuration, but it does not explicitly state when to use it versus alternatives or when not to use it. Usage is inferred from the listed record types, which is adequate but not explicit.

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