Evaluate SPF

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false. The description adds valuable behavioral detail beyond that: it discloses that DNS lookups are checked against the limit of 10, that void lookups and syntax are examined, and that a provided IP changes the result to what a receiver would see. No contradictions.

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?

A single, front-loaded sentence that packs in every meaningful detail without fluff. Each listed element (include tree, DNS lookups, void lookups, syntax, result, mechanism) contributes directly to understanding tool behavior.

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 annotations already cover safety and the output schema presumably documents return values, the description is nearly complete. It fully scopes what is evaluated and the effect of the IP parameter. The only real gap is the sender parameter, which is left unexplained in both schema and description.

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 covers 2 of 3 parameters (domain and ip), leaving sender undescribed. The description adds meaning to ip ('with ip the result a receiver would reach') and implies domain as the target, but does not explain sender's role at all. It partially compensates for schema gaps but not fully.

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 uses a specific verb ('Evaluates') and resource ('a domain's SPF'), then enumerates exactly what 'in full' means: include tree, DNS lookup count, void lookups, syntax, and the receiver result with an IP. This clearly distinguishes it from sibling tools like check_dkim or dns_lookup.

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 purpose is obvious from the name and description, but there is no explicit guidance about when to use this tool versus alternatives such as check_dkim or dns_lookup. No exclusions or alternative recommendations are given; usage is only implied.

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