update_invoice

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

Annotations already mark this as a mutating but non-destructive operation. The description adds valuable behavior beyond that: once an invoice is issued and numbered, Spanish rules lock certain fields, and Quipu returns an error when a locked field is modified. This sets expectations for conditional failure and legal constraints.

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?

Two sentences: the first states the operation clearly, the second adds the most important caveat. No filler or repetition of schema 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?

For a simple 5-param mutation tool with no output schema, the description covers what the tool does and a key failure mode. It doesn't describe the success return value, but that is not essential for correct invocation. The annotations cover the read/destructive axis, so overall context is adequate.

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?

All five parameters have schema descriptions (100% coverage), so the description does not need to explain them. It adds no parameter-specific detail beyond the schema, and the legal-lock note applies globally rather than to specific fields. Baseline 3 is appropriate.

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 ('Update') and resource ('existing Quipu invoice'). The word 'existing' distinguishes it from create_invoice, and the mutation orientation distinguishes it from get/list tools. No ambiguity about what it does.

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 gives clear context: updates are for existing invoices and are subject to Spanish invoicing rules. It does not explicitly name alternatives like create_invoice or delete_invoice, nor state when not to use this tool, but the use case is clear enough for an agent to select it among siblings.

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