Screenshot Region

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

No annotations are provided, so the description carries the full behavioral burden. It discloses the token-cost advantage, which is a useful trait, but says nothing about coordinate origin, multi-monitor/displayId behavior, resize defaults, or error conditions for out-of-bounds regions. For an 8-param capture tool with zero annotation coverage, this is a substantial gap.

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 sentences, front-loaded with the core action, then the usage/benefit rationale. No filler.

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?

Purpose, usage, and cost rationale are covered, but with no annotations and no output schema, the description should do more to disclose coordinate semantics, display targeting, and failure modes. Adequate but with clear gaps for a capture operation.

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 100%, so all 8 parameters (including maxEdge default, format enum, and displayId pattern) are already documented in the schema. Baseline 3 applies; the description adds no parameter-level detail beyond the schema.

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 ('Capture a rectangular region of the screen') that is precisely distinguishable from the sibling 'screenshot' and from screen-reading tools. An agent can immediately tell this is the region-scoped variant.

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 a clear when-to-use condition ('user points at a specific area or you only need part of the screen') and contrasts with the full-screen alternative implicitly via 'way cheaper than a full screenshot'. It does not name the sibling tool `screenshot` explicitly, so routing is strong but not fully prescribed.

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