Update Custom Cost

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

The description discloses a critical behavioral trait beyond the annotations: 'The whole cost is replaced, so send every field, not only the ones changing.' This is important for correct invocation and is not captured in the readOnlyHint/idempotentHint annotations. It also explains the endDate use case, adding practical context.

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 sentences long, front-loaded with the core action, and every clause adds value: the action, the replacement warning, and the use cases. No redundant or vague phrasing.

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?

Given no output schema and sparse annotations, the description covers the essential operational context: what the tool does, the replacement semantics, and when to use it. It lacks return-value or error-behavior details, but for an update operation with a rich schema, this is adequate. Slightly more info on request results could push it to 5.

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?

The input schema provides full descriptions for all 7 parameters (100% coverage), so the description doesn't need to explain individual parameters. It does add contextual guidance about sending every field due to replacement semantics, but this is more about overall operation behavior than specific parameter meaning.

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 clearly states 'Update a custom cost' with a specific verb and resource, and it distinguishes itself from sibling create/get/delete tools by presenting concrete use cases (fixing a wrong amount, closing an open-ended recurring cost).

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 explicitly says when to use the tool ('Use this to fix a wrong amount or to close an open-ended recurring cost by setting endDate'), which gives clear guidance for typical scenarios. However, it does not explicitly mention alternatives like create/delete for non-update cases, though sibling names make that implicit.

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