billy-mcp

approve_invoice

Destructive

Approves a draft invoice to book it permanently, transitioning from draft to approved with no option to revert.

Instructions

Approve a draft Billy invoice (draft -> approved is the only allowed state change). Approval books the invoice; it cannot be reverted to draft.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "id": "<id>"
    },
    "name": "approve_invoice"
  }
}

Input Schema

Name	Required	Description	Default
`id`	Yes	Invoice ID of a draft invoice
`verbose`	No	Return the full Billy response. Default false: compact records with key fields only (saves ~90% context)

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.3.0Jul 8, 2026

TDQS

A4.2/5.0

Behavior4/5

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

Annotations indicate readOnlyHint false and destructiveHint true, aligning with the description's statement that approval books the invoice and cannot be reverted. The description adds the irreversibility detail, though it lacks permission or side effect info.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Two sentences efficiently convey the core purpose and key behavioral constraint (irreversibility). No unnecessary words.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The description covers the essential behavioral aspect (state change and irreversibility) but does not address output format or the verbose parameter. However, given the simplicity of the tool and lack of output schema, it is mostly complete.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% with both parameters described in the schema. The description does not add meaningful parameter semantics beyond the schema, so baseline 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the verb 'Approve', the resource 'draft Billy invoice', and the specific state change from draft to approved. It distinguishes this tool from sibling tools like create_invoice or delete_invoice.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage when an invoice is in draft state and needs approval. It warns about irreversibility but does not explicitly mention when not to use or alternatives.

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