click

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

With no annotations available, the description carries the full transparency burden. It explicitly warns 'This can change app state' and discloses the 90s timeout plus caller-budget extension, which are material behavioral facts. It also explains the confirmation strategy without a follow-up snapshot. It does not cover failure modes or reversibility, but the core side effects are well disclosed.

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 short sentences, each carrying distinct value: what the tool does, how to choose the target, what side effect to expect and how to confirm, and how long it may run. No filler, no repetition of schema content, and the most important usage rule is front-loaded.

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 tool's complexity—29 parameters, many device and platform selectors, and a union target schema—the description covers the critical agent-facing concerns: state mutation risk, snapshot-preferred targeting, and timeout behavior. The output schema exists, so return values do not need elaboration. A small gap is the lack of explicit differentiation from sibling input tools like press, but this is not a blocker.

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 already documents all 29 parameters with 100% coverage, so the baseline is 3. The description adds real meaning beyond the schema by prioritizing the target union variants, telling the agent that ref/selector should be preferred and coordinates are a fallback. This is directly useful for choosing the correct target shape, justifying a 4.

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 opens with a specific verb-resource pair, 'Activate a UI target', and immediately enumerates the three supported addressing modes: snapshot ref, selector, or coordinates. This clearly distinguishes the tool's mechanism from raw gesture tools and leaves no ambiguity about what 'click' does.

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 gives explicit, actionable guidance on targeting: prefer ref/selector after a snapshot, and fall back to coordinates only when semantic targeting is impossible. It also recommends settle or verify over a follow-up snapshot after the action. It does not explicitly compare click with sibling action tools like press or longpress, so it stops short of a 5.

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