count_spf_lookups

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

Annotations already declare readOnlyHint=true, openWorldHint=true, idempotentHint=true, destructiveHint=false. The description adds concrete behavioral details: what return fields are provided (record_valid, findings, has_pass_all, etc.), the lookup counting logic, and the explicit statement that no SPF fix record is returned. This goes well beyond 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 but thorough, front-loading the purpose and return values. Every sentence adds useful information without redundancy. It could be slightly more structured, but it is efficient and clear.

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 complexity of SPF validation and the fact that there is no output schema, the description thoroughly covers all aspects: what the tool does, the two usage modes, the specific return fields, and important constraints (diagnose-only, no fix). It is complete for an agent to correctly invoke the 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?

Schema coverage is 100%, so the schema already documents both parameters. The description adds meaningful context: domain resolves the published record and counts recursively through nested includes, while record parses a pasted record counting only its own terms. This adds value beyond the schema descriptions.

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 starts with 'Validate an SPF record and count what it costs,' clearly stating the verb and resource. It lists specific return fields and explicitly distinguishes this tool from siblings by noting 'This is the SPF validator — there is no separate one.' This makes it highly specific and differentiated.

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 provides explicit guidance: 'Pass EXACTLY ONE of domain or record,' explaining when to use each. It also clarifies that this tool is 'diagnose-only' and why it does not return a fix record. While it doesn't list specific alternative tools, the usage context is clear enough.

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