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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description usefully adds what data comes back (settings, recipients, send status), but says nothing about auth requirements, error/not-found behavior, or rate limits. Adds moderate value over structured fields.

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 compact sentences with zero filler; the core purpose is front-loaded and the REST endpoint is a useful, brief trailing detail. Every clause earns its place.

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 single-parameter read-only getter with annotations covering safety, the definition is nearly complete and even hints at returned fields (helpful since no output schema exists). It only omits what happens on a missing or invalid id, a minor gap.

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% and there is only one parameter, which the schema already documents as 'The campaign id.' The description restates 'by id' without adding format, source, or lookup guidance, so 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 and resource ('Get a single campaign by id') and even enumerates the returned content ('settings, recipients and send status'), plus the underlying REST endpoint. It distinguishes itself implicitly from mailchimp_list_campaigns, but never names the sibling, so it falls short of a 5.

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 is only implied: 'by id' and 'single campaign' suggest fetching one known campaign rather than listing, but there is no explicit when-to-use, when-not-to-use, or alternative (e.g., mailchimp_list_campaigns) named. Adequate but with clear gaps.

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