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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, destructiveHint=false, openWorldHint=false), so the bar is lower. The description adds non-obvious context: the content is static, so re-calling within a session is unnecessary, and it enumerates the reference material available.

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, zero filler. The identity of the tool and the 'one call per session' constraint are front-loaded, followed by the content inventory.

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 reference tool with no output schema, the description is nearly complete: it identifies the artifact and lists the covered topics, and 'static text' hints at the return shape. An explicit pointer to the workflow step where it should be consulted would close the last gap.

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?

Zero parameters, so there is no parameter semantics to explain; the baseline of 4 applies. The description correctly avoids inventing arguments for a no-arg reference tool.

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?

Names a specific resource (the layout-format reference for Sonar screenshot sets) and states exactly what it covers: layout JSON schema, coordinate system, image handling, background shapes, fonts, translation overrides, and workflow. This is clearly distinguishable from the screenshot CRUD siblings like sonar_create_screenshot_set or sonar_update_screenshot.

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?

Explicitly tells the agent it is static text and that 'one call per session is enough', which is real invocation guidance about call frequency. It stops short of naming alternatives or stating when in the workflow to consult it (e.g., before creating a screenshot set), so it's clear but not fully routing.

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