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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds real behavioral context beyond that: a fixed 30-day lookback window, spoofing flagging of unknown senders, and the degraded fallback behavior when monitoring is disabled.

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?

Effectively one dense sentence that front-loads the report contents before the monitoring-off caveat. Every clause carries information, though the nested parenthetical makes it slightly heavy to parse.

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?

An output schema exists so return structure needn't be explained, annotations cover the safety profile, and the single required parameter is fully documented. The description still pre-summarizes the report payload, leaving nothing an agent needs to call it correctly.

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?

Only one parameter, and the schema documents it at 100% coverage (name or id, example.com). The description adds no format or syntax detail beyond the schema, so the baseline 3 applies.

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?

States a specific verb+resource (get DMARC report) and then enumerates the exact contents: senders grouped by provider, unknown senders flagged as spoofing, SPF/DKIM/DMARC pass rates over 30 days, and quarantine-readiness. This clearly separates it from enable_dmarc_monitoring and other domain 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?

Gives a concrete conditional path: when monitoring is off the tool returns the current DMARC record, and the agent is routed to enable_dmarc_monitoring to turn it on. That names an alternative with its trigger condition, though it doesn't spell out broader when-not-to-use cases.

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