fingerprint_touch

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

With no annotations provided, the description fully carries the behavioral burden. It discloses that the command reports OK even on failure, explains the enrollment ID increment issue, and details edge cases like indefinite hanging without enrollment. This goes beyond what annotations could convey.

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 moderately concise for the complexity it covers. It front-loads the core action and then adds important gotchas and troubleshooting. While thorough, it could be slightly more streamlined, but every sentence earns its place for a tool with no annotations and complex behavior.

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 no output schema and no annotations, the description is remarkably complete. It covers prerequisites, failure modes, troubleshooting, and device constraints. For a tool with high behavioral nuance (2 params, but many edge cases), this provides all necessary context.

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, so baseline is 3. The description adds meaningful value by explaining the semantics of finger_id (must match enrolled finger, default 1, suggestion to try multiple values) and serial (target device, optional). This elevates it above baseline.

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 simulates a fingerprint-sensor touch on an emulator, specifies it drives the real biometric unlock path, and distinguishes it from alternatives like PIN fallback. The verb 'Simulate' and resource 'fingerprint-sensor touch' are specific, and the context of BiometricPrompt sets it apart from sibling 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?

The description explicitly instructs to check has_biometric_enrolled FIRST, warns about the GOTCHA with non-matching finger_id, and provides concrete troubleshooting steps (try ids 2..5, second touch, re-enrollment). It also states the tool is emulator-only, guiding when not to use it.

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