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

No annotations are provided, so the description carries the full burden. It discloses the network mechanism (Cloudflare DoH), timeout (5 s), record location (v=spf1), and parsing behavior, plus the return schema including success/error states. It would benefit from noting whether includes are resolved or just parsed, but the current disclosure is strong.

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 divided into purpose, usage, and technical details. It's a bit dense but all sentences contribute meaningful information. No fluff.

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 thoroughly specifies the CheckResult structure on both success and failure, covers network behavior, and lists use cases. It is complete for a single-parameter tool.

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?

The schema already documents the domain parameter with a full description (public FQDN, restrictions). The tool description adds no further parameter-level detail, so the baseline of 3 applies.

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 clearly states the tool's function: 'Retrieve and parse a domain's SPF record, decomposing it into mechanisms and qualifiers.' It distinguishes itself from siblings by referencing dossier_dmarc for email-auth coverage and dns_lookup for raw TXT records.

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?

Explicit usage scenarios are provided: 'verify email sender policy, debug delivery failures, or check the 10-lookup limit.' It also names alternatives: 'pair with dossier_dmarc... or use dns_lookup with type=TXT'.

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