Snapshot

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

With no annotations, the description carries the full burden and does disclose a critical behavioral trait: refs reset on every snapshot, so a new snapshot must be taken after each action. It does not mention whether the call is read-only, cost/latency, or output size limits from max_depth/max_nodes.

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?

Two tightly written sentences, front-loaded with the core action and followed by the operating rule. No filler; every clause carries information an agent needs.

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?

An output schema exists so return values needn't be spelled out, and the read-before/read-after workflow is covered. However, for a tool with three undocumented optional parameters (including truncation controls), the description leaves the agent guessing about how to shape the call.

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 description coverage is 0%, so the description must compensate for the three parameters, and it mentions none of them — 'device', 'max_depth', and 'max_nodes' are entirely unexplained. This is a meaningful gap since max_depth/max_nodes likely control truncation behavior an agent needs to know about.

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 and resource — 'Get an accessibility-tree snapshot of the current screen' — and enumerates what the result contains (text, role, ref id). This makes it clearly distinguishable from the sibling 'screenshot' (pixels) and from action tools like tap/scroll.

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?

Gives explicit workflow guidance: 'read it before acting, and take a fresh one after any action since refs reset on every snapshot.' It does not state when to prefer 'screenshot' or 'wait_for_text' instead, so the alternative-selection guidance is incomplete.

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