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

With no annotations provided, the description carries the full burden. It explicitly states 'Read-only; price 0.0 (free)' and details the parsing behavior (all-qualifier strict/softfail/neutral/pass, includes). It does not mention potential DNS failures or rate limits, but for a read-only network operation, the disclosed behavior is strong.

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 two sentences, front-loaded with the core action and outputs, followed by input flexibility and cost/safety. Every sentence earns its place with no redundant or promotional content.

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?

Although there is no output schema, the description enumerates the key return elements (presence, raw record, all-qualifier, includes), which is essential for a tool with no structured output definition. It covers input forms, method (DNS-over-HTTPS), and cost. It could mention error behavior, but the essential context is present.

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 baseline is 3. The description adds the phrase 'Accepts a bare domain or a full email address,' which is already implied by the schema descriptions for 'email' and 'domain.' Thus, the added value is marginal.

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 ('Fetch and parse') and resource ('SPF policy from domain TXT records'), and enumerates the exact outputs: presence, raw record, all-qualifier, includes. This clearly distinguishes it from sibling tools like email_verify_check_mx (MX records) and domain_intel_email_auth_check (broader auth checks).

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 states the input flexibility ('Accepts a bare domain or a full email address') and the read-only/free nature, giving clear context for when to use it. However, it does not explicitly name alternative tools or exclusion criteria, though the purpose is sufficiently specific to make usage context clear.

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