Capture UI baseline

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

Annotations cover the safety profile (readOnlyHint=false, destructiveHint=false, openWorldHint=true), and the description adds real behavior: the return payload is a text summary listing title, console errors, failed requests, overflow and a11y violations, and the image only comes back on the first capture of a label or with includeFull=true. It stops short of saying whether re-capturing a label overwrites the stored baseline, which is the one mutation detail still missing.

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?

Three tight sentences, front-loaded with what it does, then the return shape, then the call-ordering rule. No filler and no repetition of schema content.

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?

With 8 parameters, 88% schema coverage and no output schema, the description usefully fills the return-value gap by naming the summary fields. Everything an agent needs to call it correctly at the right moment is present.

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 coverage is 88%, so the schema already documents most parameters and the baseline of 3 applies. The description earns the bump by clarifying includeFull's conditional semantics (image returned only on first capture of a label or when includeFull=true) beyond the schema's bare 'Also return the full screenshot'.

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?

Specific verb+resource: screenshots a page and persists it as the baseline for a label. It also implicitly distinguishes itself from ui_diff by framing itself as the producer of the artifact ui_diff consumes.

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?

Explicit sequencing guidance ('Call this BEFORE editing so ui_diff has something to compare against') names the sibling alternative and the condition that requires this tool first. That is the exact routing information an agent needs.

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