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

Annotations only supply readOnlyHint=false and destructiveHint=false; the description goes well beyond them by stating partial-update semantics ('Only the fields you pass are changed'), reversibility ('every change is reversible by calling this again with the old values'), and, most valuably, that paid-feature refusals come back from the plan and should be 'pass[ed] back as written.' That last point is real behavioral guidance an agent cannot get from 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?

Three sentences, front-loaded with the mutation scope, then the partial-update/reversibility semantics, then the routing exclusion and the plan-refusal rule. No sentence is filler and each adds a distinct, decision-relevant fact.

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 26-parameter partial-update tool with 100% schema coverage and no output schema, the description supplies the mutation semantics, reversibility, sibling routing for on/off, and plan-refusal handling an agent needs. The only gap is not addressing the overlapping set_* siblings, which is a genuine but secondary omission.

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 every one of the 26 properties is documented in-schema, including enums and paid-feature flags, so the schema carries the parameter burden. The description's field list (name, keywords, DM, link button, public reply, follow-up) lightly mirrors that without adding syntax, formats, or default semantics beyond it.

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?

Opens with a specific verb+resource ('Changes the settings of an existing campaign') and enumerates the field families it touches (name, keywords, DM, link button, public reply, follow-up). It also explicitly distinguishes itself from campaigns_pause/campaigns_resume, so an agent can separate it from the most confusable siblings without opening a schema.

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?

Gives an explicit when-not with the correct alternative: 'It cannot switch a campaign on or off — use campaigns_pause and campaigns_resume for that.' However, it is silent on the many overlapping set_* siblings (campaigns_set_public_reply, campaigns_set_links, campaigns_set_trigger, campaigns_set_keyword_buttons, campaigns_set_steps), whose fields this tool also appears to change, leaving that routing ambiguity unresolved.

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