network_spf_record_checker

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

Description goes beyond annotations by detailing that the tool performs a live DNS query (may use a remote worker), results are non-constant, no auth required, and rate limits (10 req/min, 60/hr, 200/day for anonymous, CAPTCHA above 30/hr). Annotations indicate openWorldHint=true but not specifics; the description adds valuable behavioral context without contradicting 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 and well-organized, starting with purpose, then actions, alternatives, and behavioral notes. It is a single paragraph but front-loads key information. Minor improvement could be using bullet points for rate limits, but overall it is efficient.

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 tool complexity (two actions, DNS query vs. offline parsing), the description covers purpose, operations, alternatives, behavioral traits, rate limits, and outlines return values (SPF record, matching records, multiple-record flag, parse results). With an output schema present, this is sufficiently complete.

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?

Input schema has 100% description coverage with clear explanations for each parameter (domain, action, record, worker_id). The main description does not add significant extra information beyond the schema, so baseline of 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 tool's purpose: 'SPF Record Checker. Look up and validate a domain's SPF (Sender Policy Foundation) TXT record for email authentication and anti-spoofing.' It specifies two actions (lookup and parse) and differentiates from sibling tools like network_dmarc_record_checker and network_mx_record_lookup, making the purpose distinct and unambiguous.

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 guidance is provided: 'Use network_dmarc_record_checker instead for DMARC alignment/reporting policy, or network_mx_record_lookup for mail-server MX records; this tool only handles SPF.' It explains when to use each action and mentions that domain is required for lookup but ignored for parse, giving clear context for selection.

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