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

Annotations already declare readOnlyHint=true, so the safety profile is covered; the description adds real value on top: values may be redacted depending on the key's permissions, and the tool maps to GET /api/v1/projects/{projectRef}/envvars/{env}. It does not describe ordering or pagination, but for a small config list that is minor.

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 front-loaded, then the redaction caveat, then the read-only constraint. The trailing endpoint citation is mildly redundant but is compact and aids traceability; nothing else is wasted.

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 two-parameter read-only list with full schema coverage, existing annotations, and no output schema, the description covers everything an agent needs: what it returns in principle, the redaction caveat, and the absence of write capability.

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% with an enum on environment and a documented project_ref format, so the schema carries parameter semantics. The description adds nothing about parameter format or constraints, which is the expected baseline when the schema is this complete.

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 ('List the environment variables configured for a project environment'), and the resource is unique among siblings that all concern runs, queues, schedules, and deployments. An agent can pick this tool without opening the schema.

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?

Usage context is clear (listing env vars for a given project/environment) and it explicitly rules out a class of alternatives by noting no env-var writes exist on this server, which stops an agent hunting for a write sibling. No explicit when-not or named alternative is given, but there is no overlapping sibling to disambiguate.

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