generate_spf

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

Annotations declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, and the description aligns by stating 'Nothing is looked up or stored — this is computation only.' It adds critical behavioral context about the 10-lookup limit, nested lookups, and the fact that the direct count may not reflect final validation, all beyond the 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 thorough yet tightly organized: purpose first, then parameter explanation, then limitations and alternatives, and finally return values. Every sentence adds value, with no redundancy or filler. It is front-loaded with the core purpose and then layers details logically.

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 complex tool like SPF generation, the description covers everything an agent needs: what it returns (record, direct lookup count, limit flags, warnings, DNS entry), the 255-character and 10-lookup constraints, nested lookup caveats, and clear routing to sibling tools. No output schema exists, but the description compensates fully.

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%, but the description enriches every parameter: it explains what each mechanism type means (include, ip4/ip6, useMx/useA), gives concrete examples (Google Workspace, Microsoft 365, SendGrid), clarifies policy semantics (fail vs softfail vs pass), and warns about the ten-term limit. This goes far beyond the schema's property descriptions.

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 builds an SPF record, a DNS TXT record, and specifies its function. It distinguishes itself from siblings like check_spf and flatten_spf by naming them and their purposes, making it unambiguous which tool to pick.

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?

It explicitly states when to use this tool versus alternatives: use check_spf to validate a live record, and flatten_spf only when an existing record exceeds the limit. It also explains the policy options and the importance of validating the final record, giving clear context for when this builder is appropriate.

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