check_dmarc

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

Given no annotations, the description fully carries the burden. It declares 'Read-only', 'Single GET, no auth, no side effects', and describes return values (parsed tag map, policy strength, warnings). There is no contradiction with any 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 concise: two sentences covering functionality, return values, usage guidance, and behavioral traits. It is front-loaded with the core action. Could be slightly more structured, but overall efficient.

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?

Despite lacking an output schema, the description explains the parsed tags and warnings returned. It covers prerequisites (domain), operation (fetch and parse), and results, making it complete for an agent to select and use 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%, so the baseline is 3. The description adds context by specifying that the 'domain' parameter is for checking the _dmarc TXT record, which reinforces the tool's purpose beyond the schema description.

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 specifies a precise action ('Read-only fetch and parse of the _dmarc TXT record') and lists detailed return values. It distinguishes itself from the sibling tool 'check_sender_requirements', which provides a combined pass/fail verdict.

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 explicitly states when to use this tool ('Use for DMARC policy review') and directs agents to an alternative ('use check_sender_requirements for combined Google/Yahoo SPF+DKIM+DMARC pass/fail verdict'). This provides clear decision guidance.

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