billy-mcp

list_contact_persons

Read-only

Retrieve the list of invoice recipients (names and emails) for a specific Billy contact.

Instructions

List contact persons (names/emails used for sending invoices) belonging to a Billy contact.

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": {
      "contactId": "<contactId>"
    },
    "name": "list_contact_persons"
  }
}

Input Schema

Name	Required	Description
`page`	No	Page number (1-based)
`verbose`	No	Return the full Billy response. Default false: compact records with key fields only (saves ~90% context)
`pageSize`	No	Records per page (max 1000, default 50)
`contactId`	Yes	Parent contact ID

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.3.0Jul 8, 2026

TDQS

B3.4/5.0

Behavior3/5

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

Annotations already declare readOnlyHint=true, indicating a safe read operation. The description adds minimal context about invoice-related data but does not disclose pagination behavior or sorting. No contradictions.

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?

The description is a single, efficient sentence with no wasted words, front-loaded with the key action and resource.

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

Completeness2/5

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

With no output schema, the description should explain return value structure. It hints at names/emails but lacks specifics. Pagination details are only in schema, not explained in context.

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 description coverage is 100%, so the description adds no additional meaning beyond the existing parameter descriptions. Baseline 3 applies.

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 'list', the resource 'contact persons', and the scope 'belonging to a Billy contact'. It distinguishes from sibling tools like list_contacts by specifying the sub-resource.

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

Usage Guidelines2/5

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

No guidance is provided on when to use this tool versus alternatives such as list_contacts or other listing tools. There is no mention of prerequisites or conditions.

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