check_ptr

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint, so the description does not need to restate safety. The description complements these by clarifying the tool targets mail servers and is part of an audit workflow, though it could have mentioned caching behavior (force_refresh) or rate limits.

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 only two sentences, with the core purpose immediately front-loaded in the first sentence and additional audit context in the second. Every word earns its place; no fluff or redundancy.

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 simple DNS lookup tool with a clear schema and an output schema available, the description is adequately complete. It clearly identifies the tool's domain (mail servers) and place in the audit, though it could briefly mention that force_refresh invalidates cache to set expectations about response freshness.

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%, with clear descriptions for each parameter (e.g., domain, format, force_refresh). The description adds no additional context beyond what the schema supplies, so a baseline score of 3 is appropriate.

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 a specific verb ('Verify') and resource ('forward-confirmed reverse DNS (PTR/FCrDNS) for mail servers'). It distinguishes from numerous check_* siblings by naming the exact DNS record type and use case. The phrase 'Part of the scan_domain audit' adds scoping context.

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 provides no guidance on when to use this tool versus the many sibling tools like check_mx or check_spf. The only contextual hint is 'Part of the scan_domain audit,' but there is no explicit 'use when' or comparison to alternatives, leaving the agent to guess when this specific check is required.

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