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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=false and destructiveHint=false, so the safety profile is covered. The description adds real context beyond that — counters are persisted-only, missing metrics return null, and no meeting/conversion data is fabricated — but says nothing about scoping, pagination, or what happens when neither identifier is supplied.

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?

Three short sentences, front-loaded with the core behavior and no filler. The 'APP:' prefix is noise, but otherwise the text is tight and earns its space.

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 shape needn't be explained, and annotations carry the safety profile. What remains missing is the identifier semantics and any routing hint among the many campaign siblings, leaving the definition adequate but incomplete for a two-optional-param analytics tool.

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 0% for two optional, mutually ambiguous identifiers ('id' and 'campaignId'), and the description does not mention either one. An agent has no way to learn whether these are aliases, whether one is required in practice, or which takes precedence — a significant gap the description should have filled.

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 verb and resource ('Returns persisted outbound email campaign counters'), which is clearly more precise than a tautology. However, it never distinguishes itself from close siblings like get_campaign, get_campaign_status, or get_usage, so an agent cannot tell from the text alone which analytics surface to pick.

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?

There is no statement of when to call this versus the many sibling read tools (get_campaign, get_campaign_status, get_usage), and no prerequisites or exclusions are given. The only guidance-adjacent content is a data-fidelity caveat, which is not usage guidance.

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