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

Annotations already cover the safety profile (destructive, non-idempotent, openWorld), but the description adds the top-level precondition and side-effect context not present in structured fields. It also clarifies the default-color behavior and the returned id. It does not elaborate on the destructive nature beyond the precondition, so 4 rather than 5.

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?

Front-loaded with the core action, followed by parameter sourcing and then constraint/alternative guidance in a logical flow. Every sentence earns its place; nothing is redundant with the structured fields.

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 creation tool with an output schema, the description covers everything needed: what it does, required vs optional inputs, sourcing of view_ids, the top-level precondition, and the fallback path via xtiles_move_pages. Return values are covered by the output schema.

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%, so the schema already documents all four parameters in detail, making 3 the baseline. The description adds marginal value by pointing to xtiles_get_project_structure as the source for view_ids, but its "Omit color to use the app default" phrasing is slightly looser than the schema's "no colour set (not the same as DEFAULT)" clarification.

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 ("Group existing pages together in the tab bar") with clear scope. It is immediately distinguishable from siblings like xtiles_move_pages and xtiles_update_page_group, which it names as different operations. No ambiguity about what the tool creates.

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 states the precondition (each page must be at the top level of the tab bar) and routes the agent to xtiles_move_pages when the page is already grouped. It also names xtiles_update_page_group for later recolouring, so the when/when-not/alternative guidance is complete.

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