email_auth

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

Discloses read-only nature, no API key requirement, rate-limiting, and output format: 'Returns a text report: score, per-mechanism KPIs, issues, and actions.' No annotations provided, so description carries full burden and does so thoroughly.

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?

Description is a single paragraph but efficiently structured: front-loads purpose, then lists mechanisms, usage guidance, alternatives, and limitations. Slightly lengthy but each sentence adds value; no fluff.

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 complexity (multiple checks, scoring) and no output schema, description explains return value in detail: '0-100 deliverability score... text report: score, per-mechanism KPIs, issues, and actions.' Covers all necessary context for an AI agent to understand behavior.

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% for the single parameter 'domain'. Description adds meaning beyond schema: specifies format (part after '@'), example, and accepts IP for reverse/PTR checks. This clarifies usage beyond simple schema definition.

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 its purpose: 'Assess a domain's email authentication and deliverability posture' and lists specific mechanisms (MX, SPF, DMARC, etc.). It distinguishes from siblings like dns_lookup and email_header_analysis by specifying focus and scope.

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 usage guidance: 'Use this for a full sending/receiving readiness review of a domain.' Also provides when-not and alternatives: 'Use dns_lookup instead if you only need raw TXT/MX records, or email_header_analysis to diagnose a specific message that was already sent.'

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