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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false, and destructiveHint=false, so the safety profile is covered. The description adds useful context that results contain pass/fail counts for IPs and hostnames, but it does not mention pagination, ordering, or how date-range filters affect aggregation.

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?

A single front-loaded sentence with no filler or repetition. It is appropriately sized for a simple list tool.

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 read-only list tool with no output schema, the description should clarify return shape more than 'pass/fail counts' – for example grouping, pagination, and date-filter behavior. It is broadly adequate but leaves meaningful gaps for an agent interpreting results.

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 id, from, and to are fully documented in the schema. The description adds no parameter-specific meaning such as date-range semantics or whether id is required, so the baseline 3 applies because the schema does the heavy lifting.

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 the resource is 'sending sources (IPs and hostnames) seen in DMARC reports' and that output includes pass/fail counts, which distinguishes it from siblings such as list-dmarc-asns, list-dmarc-countries, and list-dmarc-reporters. However, it relies on the tool name for the 'list' verb and does not explicitly state that results are scoped to a single domain.

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?

Provides no when-to-use guidance, no exclusions, and does not name sibling alternatives such as list-dmarc-reporters, list-dmarc-asns, or list-dmarc-countries. Usage is only implied by the resource name.

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