ax_set_value

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

With no annotations, the description carries the full burden and delivers useful traits: background execution, no cursor movement, legacy status, and fail-closed behavior on ambiguous substring matches. It omits permission requirements and what a successful/partial set reports.

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 dense sentences with the operation, its safety behavior, and the alternative all front-loaded; no filler. The closing advisory is slightly terse but 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 no-annotation, no-output-schema mutation tool, the description covers mechanism, side-effect profile, and failure semantics well. It could still say more about permissions and post-condition reporting, but nothing critical is missing.

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 coverage is 100%, so the baseline is 3, but the description adds real meaning beyond the schema by explaining that ambiguous substring matches against `query` fail closed rather than picking arbitrarily.

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 (sets) and resource (a control value) plus the underlying mechanism (macOS Accessibility / Windows UI Automation). 'Legacy query action' and the reference to ax_read make it distinguishable from the many sibling click/read/type tools.

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?

Explicitly steers the agent away from this tool in favor of 'a fresh ax_read node whenever possible,' signaling a deprecation/preference order. It stops short of spelling out the conditions under which this legacy path is still required.

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