get_env_var

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

No annotations are provided, so the description must fully disclose behavior. It does not state what happens if the variable is unset (e.g., returns null, undefined, or errors), whether it returns a string or other type, or any side effects. Given the lack of annotations, this is a significant gap.

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?

The description is a single, concise sentence that directly conveys the purpose with no redundancy or unnecessary detail. It is front-loaded and every word 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 read-only tool with one parameter and 100% schema coverage, the description is minimal but sufficient to convey basic intent. However, with no annotations, the lack of behavior for edge cases (e.g., unset variable) reduces completeness. An output schema exists, reducing the need to describe return format, so this is adequate yet not rich.

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%, so the parameter 'name' is already documented in the schema. The description adds no further semantics beyond what is provided. Baseline 3 is appropriate as the schema covers the parameter fully.

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 tool's purpose: 'Return the value of an environment variable.' It uses a specific verb ('return') and resource ('environment variable'), distinguishing it from siblings that operate on files or run commands. Although it lacks explicit mention of scoping (e.g., whether it works across sessions), the purpose is unambiguous.

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 description implies when to use the tool (to retrieve an environment variable's value) but does not provide guidance on when not to use it or alternatives. It does not mention any prerequisites or context (e.g., whether the variable must be set beforehand or if it works in the same session). This is adequate but lacks explicit usage exclusions.

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