check_spf

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

Annotations already indicate readOnlyHint, idempotentHint, and destructiveHint. The description adds that it flags syntax errors and shows trust surface. It also notes the force_refresh parameter bypasses cache, which is useful behavioral context. No contradiction with 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?

Two sentences: first covers purpose and output, second gives usage context and tool relationship. No wasted words. Very efficient and well-structured.

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?

The description fully covers what the tool does, when to use it, and its relationship to the audit. Given the presence of an output schema (mentioned in context), return values are handled. No gaps for a lookup 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 description coverage is 100%, so the parameters are fully documented in the schema. The description adds no new parameter details beyond what's in the schema, except implicit context from the overall description. Baseline 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 clearly states the verb 'look up and validate' and the resource 'SPF record for a domain'. It lists specific outputs (IP addresses, third-party senders, syntax errors, trust surface) which distinguishes it from sibling tools like check_dmarc or check_dkim.

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 says 'Use when you need to know who is permitted to send email as a domain', giving a clear usage context. It also mentions being part of scan_domain audit, but does not explicitly exclude alternatives. The sibling list provides many other email security checks, so the agent can infer when not to use.

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