check_spf

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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds genuinely new behavioral context not in annotations: the tool both validates and flags misconfigurations, and it costs no verification credits — a meaningful constraint for an open-world network lookup tool.

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 compact sentences with zero filler; the core action is front-loaded and the cost note follows as supporting context. Every clause earns its place.

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 single-parameter read-only lookup with annotations and no output schema, this is nearly complete. The only soft gap is that it doesn't characterize the response (e.g., whether it returns pass/fail plus a list of specific issues), which an agent might want to know when composing follow-ups.

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?

There is only one parameter (domain) and schema description coverage is 100%, with the schema already giving the example 'example.com'. The description adds no format or constraint detail beyond the schema, so the baseline 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?

States a specific verb and resource (check a domain's SPF record) plus the outcome (flag common misconfigurations). The SPF-specific framing naturally distinguishes it from siblings like check_dmarc and check_dkim, though no sibling is named explicitly.

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?

Usage is only implied by the resource name — an agent can infer this is the SPF-specific check versus check_dmarc/check_dkim/check_mx. There is no explicit when-to-use, prerequisite, or routing guidance, and no mention of check_domain_health as the aggregate alternative.

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