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

The annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is clear. The description adds value by specifying that the tool analyzes the SPF include chain, which is a specific behavioral trait not captured in structured data. No contradictions with 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 two sentences plus a brief note—no wasted words. The first sentence front-loads the primary purpose, followed by usage guidance in the second, and ends with the audit context. 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 existence of an output schema (specifies return values) and thorough annotations (safety, idempotency), the description covers the essential context: what the tool does, when to use it, and its role in a broader audit. It does not explain integration with related sibling tools like resolve_spf_chain, but that is not critical for basic selection.

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 does not add additional meaning beyond what the schema already provides for the three parameters (domain, format, force_refresh). It mentions 'SPF include chain' contextually but does not elaborate on parameter details or constraints.

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 detects 'SubdoMailing risk' by analyzing the SPF include chain for dangling or hijackable subdomains. This specific verb+resource combination distinguishes it from sibling tools like check_subdomain_takeover and check_spf, which cover related but distinct concerns.

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 explicitly tells the agent when to use this tool: 'when you want to know if an SPF include chain can be hijacked through a dangling domain, or to detect subdomain mailing risk hidden in SPF includes.' It also notes it's part of the scan_domain audit, providing context. It does not explicitly name alternatives for when not to use it, but given the sibling list, the usage scope is well-defined.

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