set_variable_value

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

The description discloses that this tool mutates a variable's value (set operation), matching the annotations (non-read-only, non-destructive). It also details the valid value formats and the return object structure, compensating for the lack of an output schema.

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 two sentences with no wasted words. It efficiently communicates the essential information without repetition or filler.

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?

Given the absence of an output schema, the description fully specifies the return shape. It also covers prerequisites, value constraints, and the relationship between variableId and modeId, making the tool self-contained.

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 covers 100% of parameters with descriptions. The description adds value by explaining that value must match the variable's resolvedType, providing concrete examples, and clarifying that modeId comes from the variable's collection.

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'), the resource ('a variable's value for one mode'), and the scope. It distinguishes from sibling tools such as create_variable and delete_variable by focusing on value assignment.

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 explicitly states the prerequisite 'Create the variable first with create_variable,' guiding the agent on when to use this tool. It does not list explicit alternatives for when not to use it, but the context is clear enough.

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