voltage_capture

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the description's job is to add behavioral context. It does so by specifying 'return it to you directly' and explicitly noting it does not use the local vision model—information not in annotations. No contradictions exist.

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 tightly written: a clear one-sentence purpose, a brief usage block, and a one-line parameter definition. No fluff or redundancy. The key purpose is front-loaded, and every sentence contributes value.

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 simple screenshot tool, the description covers usage, region format, and direct return. However, the `max_width` parameter remains unexplained; an agent might not know how to set it or its effect on output. Given that the tool has no output schema, a bit more detail on max_width would make it fully complete.

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 description explains the `region` parameter fully: it is [x, y, width, height] in desktop pixels and can be omitted for the whole desktop. However, `max_width` is not described at all; the schema only shows it is an integer with default 1280. Since schema description coverage is 0%, the description should compensate for both parameters, but it only covers one.

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 opening sentence 'Take a screenshot and return it to you directly' uses a specific verb and resource, and clearly states the result. It also distinguishes itself from the vision-model-based sibling by saying 'This does not involve the local vision model,' which makes its purpose unambiguous.

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?

It provides concrete use cases: 'before writing a Playbook, to pick coordinates for probes and click regions, or to work out why a run went wrong.' This tells the agent exactly when to invoke it. It does not explicitly mention alternatives or when not to use it, but the context is clear enough to guide selection.

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