network_mx_record_lookup

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

The description discloses that each call issues a fresh DNS query (non-idempotent), matching the idempotentHint=false annotation. It also reveals rate limits (10/min, 60/hour, 200/day) and CAPTCHA-gating, which annotations do not cover. No contradictions.

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 well-structured with front-loaded purpose and usage, then behavioral details. It is slightly verbose but every sentence adds value. Could be slightly tighter but still effective.

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 presence of an output schema (not shown), the description does not need to detail return values. It covers purpose, usage guidelines, behavioral traits, and rate limits. Complete for a lookup tool.

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%, so baseline is 3. The description adds minimal semantic value beyond the schema: it confirms 'action' only supports 'lookup' and domain note. No additional parameter context.

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 it performs MX record lookup for a domain, returning mail servers and priorities. It distinguishes itself from siblings like network_dns_lookup (for arbitrary record types) and network_spf_record_checker/network_dmarc_record_checker (for email-auth policy).

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 states when to use this tool ('for the email-delivery path of a domain') and when not to, pointing to alternative tools for other record types or email-auth policies.

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