ax_set_value

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

Discloses key behavioral traits: background operation, no cursor, platform-specific behavior (macOS works, Windows returns error), and targeting the last window-captured app. No annotations are provided, so the description carries the full burden.

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?

Four sentences, each providing essential information: purpose, usage context, parameter explanation, and target scope. No redundancy or extraneous detail.

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?

Covers platform, behavior, and parameter details. Lacks explicit description of the return value, but for a mutation tool, this is generally acceptable given the simplicity of the tool.

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 covers both parameters with descriptions. The description adds an example of use (filling a text field without focusing) and clarifies the matching logic (case-insensitive substring). This adds minor value beyond the schema.

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?

Clearly states the tool sets a control's value via the OS accessibility tree, with a concrete example (filling a text field without focusing or typing). It distinguishes itself from siblings like type_text by emphasizing background operation and no cursor.

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?

Provides context on when to use (background value setting without focusing) and platform limitations (macOS only, Windows returns error). However, it does not explicitly mention alternatives or when not to use.

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