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

Annotations already convey idempotent and non-destructive traits. The description adds useful behavioral context: the variable is 'rolled out' and secret-looking keys are rejected. No contradiction with annotations, and the extra details go beyond what structured hints provide.

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 with no fluff. The first sentence states the action, the second explains when to use, the third explains when not to use. Every sentence 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 simple setter with full annotations and no output schema, the description covers purpose, usage, and limitations. A minor gap is not specifying overwrite semantics or rollout side-effects, but this is not critical for a straightforward environment variable set.

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 covers 100% of parameters with descriptions. The description enriches this by giving examples of acceptable keys (LOG_LEVEL, feature flag) and explicitly ruling out secret values, adding practical meaning to the 'key' and 'value' parameters.

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 clearly states 'Set a single environment variable on an app and roll it out,' which is a specific verb+resource action. It also distinguishes from sibling tools like deploy_app or list_apps by focusing on environment variables.

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?

Provides explicit when-to-use guidance: 'Call this when an app needs plain configuration such as LOG_LEVEL or a feature flag.' Also gives a clear exclusion: 'For secrets... use the Secrets section... this tool rejects secret-looking keys.' This fully addresses when and when-not to use the tool.

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