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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the safety profile is covered. The description adds non-obvious behavioral context—specifically that multiple SPF records cause receivers to treat the domain as unprotected—which enriches the agent's understanding beyond a simple read operation.

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?

At roughly 65 words, the description is reasonably tight and front-loads the core purpose ('SPF record and how strict it is') before explaining the return values and usage. The opening fragment is slightly informal and could be trimmed, but overall every sentence 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?

Given the low complexity (one parameter, read-only lookup) and the existence of an output schema, the description is thorough. It covers the purpose, key return values, an error condition, and the primary use case. No critical behavioral detail is missing for an agent to call this correctly.

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 coverage is 100% with a well-documented `domain` parameter, including a helpful note that a full email address is accepted. The description adds no parameter-specific detail beyond the schema, so a baseline of 3 is appropriate since the schema carries the load.

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 states a specific verb ('Returns') with a clear resource (SPF TXT record, `all` qualifier, multi-record status). It clearly differentiates from siblings like get_dmarc_record and get_mx_records by focusing specifically on SPF semantics and its strictness qualifier, so an agent can tell them apart without opening schemas.

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?

Explicitly says 'Use when diagnosing why mail from a domain is being rejected or marked,' giving clear context for invocation. It stops short of naming sibling alternatives and when NOT to use this tool, but the usage context is concrete and actionable.

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