Comments: add comment to transaction or receipt

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

The description discloses that this is a write operation that is not idempotent ('calling twice may create duplicates'), which aligns with the idempotentHint:false annotation but adds specific consequence. It also reveals the lack of read/edit/delete endpoints, which is not apparent from annotations. These are valuable behavioral insights beyond what annotations provide.

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 somewhat verbose, starting with a generic '🟡 WRITE · creates data' block that applies to all write tools, then repeating the title. However, the key information (exactly-one constraint, limitation) is clearly presented. The structure is acceptable but could be tightened by removing the generic header.

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 description covers the required parameter constraint, the use case, and the persistence limitation. It doesn't describe the output, but an output schema exists. For a simple comment-adding tool, the description is sufficiently complete, though it could mention error scenarios or the expected response format.

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%, but the description adds the critical mutual exclusivity rule: exactly one of transaction_id_by_customer or receipt_id_by_customer must be set. The schema merely lists them as optional, so the description provides essential semantics that prevent invalid calls. This goes beyond the schema documentation.

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 the tool's purpose: 'Add comment to transaction or receipt.' It identifies the specific resource (comments) and the action (add), and provides a concrete use case ('record why a booking was categorised'). This distinguishes it from sibling tools that create other entities like transactions or receipts.

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 specifies the required condition: 'Exactly one of transaction_id_by_customer or receipt_id_by_customer must be set.' It also notes the limitation that v1 offers no read/edit/delete endpoints, so comments are only visible in the web app. While it doesn't explicitly say 'use this instead of X', the context is clear and the constraint is actionable.

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