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

Annotations already flag destructiveHint=true and idempotentHint=false, so the bar is lower and the description still adds real value: it discloses that content/recipients are wholesale replacements, that at least one audience must remain, and that prior values are unrecoverable. It does not say what happens when the campaign is not a draft (error vs. ignored) or what the response contains.

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 tight sentences with zero filler, leading with the scope restriction and following immediately with the destructive replacement semantics. Every clause carries information an agent needs before calling.

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 an 18-parameter destructive mutation with no output schema, the description covers the highest-risk behaviors (replacement, irreversibility, audience minimum) but says nothing about the failure mode for non-draft campaigns or what a successful update returns. Adequate to call safely, incomplete for an agent predicting outcomes.

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 67%, above baseline, and the description adds semantics the schema lacks: content overwrites the body rather than merging, recipients overwrites the whole audience list, and an at-least-one-audience constraint that appears nowhere in the schema (recipients has no minItems). The remaining 15 parameters (ab_test, utm_params, tracking overrides) are left entirely to schema text.

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 plus a scoping constraint: only *draft* campaigns are updatable, which inherently separates it from send-campaign, cancel-campaign, and delete-campaign. It stops short of naming any sibling explicitly, so an agent must infer the routing itself.

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?

The 'draft campaign' qualifier implies when this is legal and the replacement rules imply when to include content/recipients, but there is no explicit when-to-use, when-not, or pointer to alternatives such as create-campaign or update-email. Usage is inferable rather than stated.

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