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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds real context beyond that: the 30-day measurement window, the exact metrics returned, and the precondition that the workspace must have subscribed contacts. It doesn't discuss auth or rate limits, but those are not central for a read tool.

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?

Two tight sentences with zero filler: the first front-loads what the tool returns, the second front-loads the when-to-use directive and the scope restriction. Nothing is repeated from the schema or annotations.

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 values needn't be described, and the description covers scope (30-day window), contents (metrics), usage timing, and the workspace eligibility constraint. Nothing an agent needs in order to call it correctly is missing.

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?

There is a single parameter (workspaceId) and schema description coverage is 100%, so the schema already explains what it is and when to omit it. The description adds no parameter-level guidance, which is acceptable at this coverage level but not above baseline.

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 and resource ('Sending health over the last 30 days') and enumerates exactly what is measured: sent volume, bounce, complaint and unsubscribe rates, review/pause rates, and hold-back reasons. This is clearly distinguishable from siblings like readPerformance, readSiteHealth, or readScorecard.

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?

Explicitly directs when to call it ('Check this BEFORE proposing any send') and explains the consequence of skipping it, plus the correct alternative action when a bounce problem exists ('fix deliverability rather than to mail more'). It also states the eligibility condition: only for a workspace with subscribed email contacts.

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