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

Beyond readOnlyHint=true, the description discloses the trait that matters most: the response contains plaintext secret VALUES such as API keys and database URLs. It also documents the underlying API call and the exact response envelope, which annotations do not cover.

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 short sentences: purpose first, security warning second, contract third. Every sentence carries information an agent needs and nothing is padded.

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?

No output schema exists, but the description supplies the return shape ({ variables: [{ id, name, value }] }), so the agent knows exactly what comes back. With one fully documented parameter and a declared read-only profile, nothing material is missing.

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 100% and the single 'app' parameter already documents both accepted forms (name or app-… id). The description adds no additional parameter semantics beyond the schema, so the baseline applies.

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 (list) and resource (an app's environment variables), and pins the scope to a single app. It is unambiguously distinct from the mutating sibling scalingo_set_variables and from the app-detail 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?

The secret-exposure warning gives real context for deciding whether to call this tool, effectively cautioning against casual use. It stops short of naming scalingo_set_variables as the alternative for modification, so no explicit when-not routing is provided.

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