Set env var

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

With no annotations provided, the description carries the full burden. It discloses that values are secrets/config, that they are injected on preview and deploy, and that 'Values are never echoed back'—an important non-obvious behavior. This goes beyond the schema and offers useful transparency, though it does not cover overwrite semantics or auth requirements.

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, each earning its place: the first states the action and resource, the second explains timing and a key behavior. It is front-loaded with purpose and avoids extraneous detail.

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 mutation tool with no annotations, no output schema, and 0% schema description coverage, the description is too sparse. It leaves open questions: what happens if the key already exists (overwrite?), is the app required to pre-exist, are there naming constraints, and are there any side effects. An agent might call it incorrectly without these details.

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 0%, so the description must compensate, but it only says 'secret/config value in the app's .env' without explaining the individual parameters (app, key, value) beyond their names. It does not provide formats, constraints, or interaction details, leaving the agent to infer from context.

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 the verb 'Set' and the resource '.env' for a specific app, and it explicitly mentions 'secret/config value' which differentiates it from related tools like list_env (which lists) and write_file (which writes files, not 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?

It specifies when the value takes effect ('Injected into the app's process on preview and deploy'), which gives concrete context for use. However, it does not explicitly state alternatives or when not to use this tool, though the sibling tool names (e.g., list_env) imply a read counterpart.

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