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

Annotations indicate idempotentHint=true and non-destructive. Description adds behavioral context: this is an update operation (implies mutation but safe), with channel immutability. No side effects mentioned, but sufficient for typical update.

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 sentences pack all necessary information: purpose, constraint, and usage instruction. No redundant words. Highly efficient.

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?

Given 8 parameters, nested objects, and output schema presence, the description covers essential update semantics and an important constraint. Could mention that status transitions are allowed (enum hints at this) but not critical. Good balance.

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 coverage is 100%, so baseline 3. Description adds value by explaining channelConfig structure ('For email, use subject + htmlBody...') and that only changed fields should be provided. However, recipientSource description ('segment | tier | manual') conflicts slightly with schema enum, reducing clarity.

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?

Description clearly states 'Update an existing campaign' with specific verb and resource. Also adds constraint about channel immutability and instruction to pass only changed fields, which distinguishes from create/delete siblings.

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 says 'Pass only fields to change', guiding optimal usage. Mentions channel cannot be changed, which is a when-not-to-use rule. No explicit alternatives, but sibling context provides options.

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