screenshot

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

readOnlyHint=true is consistent with a capture-only tool, so no contradiction. Beyond the annotation, the description adds genuinely useful behavioral context: the returned image defines the coordinate frame for subsequent click coordinates, which the agent could not derive from structured fields.

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 short, front-loaded sentences with no filler. The action comes first and the critical coordinate-frame caveat follows immediately.

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 zero-param read-only tool with an annotation covering safety, the description supplies purpose and the coordinate relationship. It omits capture scope (full screen vs. active window/tab), which would further sharpen correct invocation, but overall it is sufficient.

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 tool takes zero parameters and the schema is an empty object, which is the baseline-4 case. There is nothing for the description to clarify about arguments.

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?

"Take a screenshot and look at it" gives a specific verb and resource, and the follow-on sentence clarifies the intent (inspect app state). It does not, however, explicitly differentiate itself from siblings like click or list_browser_tabs, so the agent must infer the boundary.

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?

"Use this to see an app's state, then click what you see" implies the usage context (inspect before clicking), which is helpful sequencing. There is no explicit when-not guidance or named alternative, so the routing is only implied rather than stated.

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