Alignment by day

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

Annotations already declare readOnlyHint=true and destructiveHint=false, and the description adds substantial behavior on top: counts are message-weighted, the window defaults to 30 days and is clamped at 365, results are capped at 50 days with a truncated flag, and paging backward is done via day_before. This discloses the exact response-shaping and limit behavior an agent needs.

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?

Four sentences, front-loaded with what is returned (counts and dispositions) before the window rules and the paging escape hatch. Every sentence carries distinct information and there is 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 compensates by enumerating the returned fields (total, DMARC pass, DMARC fail, disposition) plus the truncated flag, and it covers defaults, clamping, and paging. An agent has everything needed to call this correctly and interpret the result.

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 the baseline is 3, and the description earns an extra point by adding parameter meaning the schema omits: the 365-day clamp, the 50-day truncation with a truncated flag, and the backward-paging pattern using day_before. It does not restate the domain filter semantics, but the schema already covers those.

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 names a specific resource and output shape: per-day message counts broken into total, DMARC pass, DMARC fail, and disposition buckets, with message-weighted semantics. That is far more specific than a tautology. It stops short of a 5 because it never contrasts itself with sibling tools like get_report_records or query_records that an agent might otherwise pick for DMARC data.

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 guidance is operational rather than selective: it explains the default 30-day window, the 365-day clamp, the 50-day truncation, and how to page backward with an earlier day_before. That is genuinely useful, but there is no statement of when to choose this tool over the sibling reporting tools, which is the main when-to-use decision an agent faces.

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