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

Annotations already declare read-only, idempotent, non-destructive, and closed-world behavior. The description adds useful behavioral detail beyond that, including output ordering (failing senders first) and duplicate-report deduplication, though it does not discuss errors, size limits, or malformed input handling.

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 front-loaded with the core action and resource, then efficiently lists the report contents and input options. Every sentence contributes useful information with no filler.

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?

With no output schema, the description adequately explains what the tool reports: passing/failing counts, alignment-only failures, quarantine/reject counts, and per-IP SPF/DKIM outcomes. A small gap remains around whether at least one input form is required in practice and how errors are surfaced.

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 both xml and gzipBase64 are already well documented. The description reinforces accepted input forms and duplicate handling, but adds little parameter semantics beyond what the schema already states.

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 states a specific verb and resource: reading DMARC aggregate (rua) reports and reporting senders, pass/fail outcomes, alignment failures, and per-IP SPF/DKIM results. This is clearly distinct from DMARC record-checking siblings, though it does not explicitly name the alternative sibling tools.

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?

Usage is implied by the resource itself: use this when you have a DMARC aggregate report to analyze. However, it does not explicitly say when to use this versus check_dmarc or check_email_authentication, nor does it state prerequisites or exclusions beyond input format notes.

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