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

Annotations already flag destructive=true, idempotent=true, and openWorld=true. The description goes beyond them by disclosing the critical whole-document semantic ('does not merge') and the auth requirement ('authorized Sonar account or a write-scope API key'), telling the agent exactly what gets destroyed. It stops short of 5 only because no rate limits or failure modes are described.

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 the core action, then the critical non-merge caveat, the review-visibility note, and the auth prerequisite. No filler and every sentence carries distinct information.

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 nested-object mutation tool with no output schema, the description covers the destructive whole-document semantics, the required authorization, and the post-call human-review consequence. Return details are unnecessary given the 'shows up immediately in Screenshot Studio' note, though error/partial-failure behavior is not addressed.

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 100% and the layout parameter's schema description already explains the full-replacement/non-merge behavior and the placeholder caveat. The description's 'whole-document replace' phrasing reinforces but does not add meaning beyond the schema, so the baseline of 3 applies.

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 ('Replace'), resource ('one screen's layout'), and scope ('in a screenshot set'), which cleanly distinguishes it from sonar_update_screenshot_set and sonar_add_screenshot. An agent can identify the operation without opening the schema.

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?

Provides a clear workflow ('fetch the current layout, modify it, send it back') that tells the agent how to invoke it correctly. It does not, however, explicitly name alternatives such as update_screenshot_set versus add_screenshot or state when not to use it, so it stops short of a 5.

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