billy_approve_invoice

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

With no annotations provided, the description fully discloses the write operation and the two-step confirmation pattern: 'WRITE — requires confirm:true. Without it, this tool returns a dry-run preview... explicit second call with confirm:true is needed to write.' This is comprehensive behavioral disclosure.

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 concise sentences front-loading the key purpose, state change, and critical behavioral requirement. No wasted words, every sentence adds value.

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 purpose, usage, and behavioral details adequately for a simple approval tool. It could explicitly state that the id must refer to a draft invoice, though this is implied by 'draft → approved'.

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 description adds significant meaning beyond the schema, explaining the confirm parameter's dual behavior: dry-run preview without true, actual mutation with true. The schema only had a basic description for confirm; the description clarifies the execution model completely.

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 explicitly states the verb 'Approve', the resource 'draft invoice', and the state change 'draft → approved'. It clearly distinguishes this tool from siblings like billy_send_invoice by stating it's required before sending or marking paid.

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 states 'Required before sending or marking paid', which gives clear context on when to use this tool. It implies not to use it on non-draft invoices, but does not explicitly name alternatives.

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