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

The readOnlyHint annotation already declares the operation is safe, and the description reinforces this with billing-specific language about not charging or changing anything. It does not add details about authentication, rate limits, or exactly what preview data is returned, but it adequately covers the key behavioral risk.

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?

The description is two compact sentences with the essential scoping and safety information front-loaded. The API endpoint detail adds minor context without disrupting conciseness.

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 complex preview tool with nested customization parameters and no output schema, the description explains the main purpose and side-effect behavior. It could say more about the shape of the returned cost/effect preview, but the core information needed to call it correctly 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 description coverage is 100%, so all six parameters are already documented in the input schema. The description adds no parameter-specific meaning beyond the schema, which is acceptable at the baseline when the schema does the heavy lifting.

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?

The description states a specific verb and resource: previewing the cost/effect of attaching a plan to a customer. It also clarifies the scope by saying this happens WITHOUT charging or changing anything, which distinguishes it from the actual attach sibling tool.

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?

The description makes clear this is for dry-run previewing before an actual attach, especially with the phrase 'WITHOUT charging or changing anything.' However, it does not explicitly name autumn_attach_plan as the alternative or state when not to use this preview tool.

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