Set Project Variable

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

The annotation already provides idempotentHint, indicating safe repeatability. The description adds that variables are accessible in expressions, which is useful context. However, it does not disclose persistence, scope, or any side effects beyond setting the variable.

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 sentence that efficiently conveys the core purpose and usage context. It is front-loaded with the action. However, it could be slightly expanded to include parameter details without becoming verbose.

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 set operation with no output schema, the description covers the basic purpose and mentions the expression syntax. However, it lacks parameter semantics and does not explain how to use the variable after setting, which an agent might need to know to leverage the tool effectively.

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?

The schema description coverage is 0%, meaning the input schema provides no parameter descriptions. The tool description also fails to describe the 'key' and 'value' parameters, leaving ambiguity about format, constraints, or allowed values. This is a significant gap.

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 action ('Set') and the resource ('project-level variable'), and mentions the specific usage context ('accessible in expressions as @key'). It distinguishes itself from sibling tools like get_project_variables (which retrieve variables) and other set tools that modify different resources.

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 the tool is for setting variables to be used in expressions, but it does not explicitly state when to use this tool versus alternatives like set_setting or when not to use it. No exclusions or comparisons with siblings are provided.

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