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

With annotations already declaring destructive/non-idempotent/not-readOnly, the description adds material context the agent cannot get elsewhere: a 422 on locked content attributes, PUT accepted alongside PATCH, admin-only authorization, and the required `whatsapp_campaigns` feature. This is exactly the extra behavioral disclosure expected on top of annotations.

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?

Front-loaded with the action, then the mutation semantics, then the most important gotcha (post-draft locking), then auth/feature caveats. Efficient overall, though the opening 'Update a campaign. Changes a campaign's attributes.' is slightly redundant.

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 nested, no-output-schema mutation tool, the description covers the critical operational facts (partial update, locking/422, admin + feature gating). It is complete enough to invoke correctly, with only the sibling ambiguity and unenumerated 50%-coverage params left unaddressed.

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?

The key semantic contribution is PATCH-style partial update ('send only the ones to change'), which clarifies the payloads for the required `id`/`whatsapp_campaign` pair. Schema coverage is only 50% and the description does not enumerate or add syntax for the remaining nested attributes, so it neither fully compensates nor is empty.

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 gives a specific verb (update) and resource (campaign) and elaborates on what 'attributes' means, including which remain editable after draft. However it never distinguishes this tool from the highly similar sibling `update_campaign`, so an agent must guess between the two.

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?

It provides strong conditional usage guidance: send only fields to change, and once the campaign leaves `draft` content attributes are locked while name/description/schedule/window/pace stay editable for slowing a running campaign. It stops short of naming alternatives such as `pause_whatsapp_campaign` or `cancel_whatsapp_campaign` for stopping rather than adjusting a campaign.

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