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

With annotations (readOnlyHint=false, destructiveHint=false, openWorldHint=true, idempotentHint=false), the agent already knows this is a mutating, non-idempotent operation. The description adds useful context by mentioning the creation of a Saved Version before the change and the 'native Fine Structure' nature. No contradiction with annotations. The side effect disclosure goes beyond annotations.

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 sentences, each carrying essential information: the primary purpose, a prerequisite workflow step, and a side effect. Front-loaded with the core action. No redundant or filler 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?

The tool is complex (7 params, nested objects, no output schema), but the schema fully documents parameters, including constraints like 'Traffic must total 100.' The description adds the critical side effect (Saved Version) and prerequisite (update_app). The only minor gap is that it doesn't state what the tool returns, but since there is no output schema, that is not mandatory.

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% (all 7 parameters have descriptions in the schema). The tool description does not add parameter-level detail; it only provides an overall prerequisite. According to the calibration, baseline 3 is appropriate when schema covers the parameters, and the description doesn't need to repeat them.

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+resource ('Create a native Fine Structure A/B test') and distinguishes from siblings like delete_ab_test, update_ab_test, list_ab_tests, and get_ab_test_stats. The description makes it clear this is about creating a test between existing app pages, leaving no ambiguity.

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 concrete prerequisite: 'Use update_app first if a variant page still needs to be generated.' This clearly indicates a common workflow step. It also notes the side effect of creating a Saved Version, which informs when to use this tool. However, it does not explicitly list alternatives or conditions when not to use it, so it falls 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.