What is billy-mcp-server CLAUDE.md?

A project instruction file for Claude Code, describing how to build, run, test, and configure a server that connects to Billy, an accounting service. It also outlines the server's code structure and supported accounting data.

Building and running the TypeScript server, starting development or watch mode, checking its Billy API connection, and working with contacts, invoices, products, payments, bills, and accounts.

It gives the coding agent the repository-specific commands, setup requirements, and environment details needed to work correctly without guessing.

billy-mcp-server CLAUDE.md — Instructions file for coding agents by markhm: A project instruction file for Claude Code, describing how…

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods

npx agentmods add instructions/markhm/billy-mcp-server/claude-md

Clone the repo

git clone --depth 1 https://github.com/markhm/billy-mcp-server

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/instructions/markhm/billy-mcp-server/claude-md.svg)](https://agentmods.dev/instructions/markhm/billy-mcp-server/claude-md)

Your own site

<a href="https://agentmods.dev/instructions/markhm/billy-mcp-server/claude-md"><img src="https://agentmods.dev/badge/instructions/markhm/billy-mcp-server/claude-md.svg" alt="Measured on agentmods" height="20"></a>

Per session 785 This file is loaded in full into every session.

When invoked 785 The same file — it is already loaded in full.

Security scan A 0 findings. Scan, not verified.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5	$0.00785	$0.00785
Opus 5	$0.00392	$0.00392
Sonnet 5	$0.00157	$0.00157
Haiku 4.5	$0.00078	$0.00078

Measured 3d ago against content hash 40209745a7b5, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

billy-mcp-server CLAUDE.md scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

CLAUDE.md · 96 lines

How it starts

The opening of the file, as written. The whole thing — 96 lines — stays where its author put it; the contents beside it link to each section on GitHub.

CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Development Commands

Build and Development

npm run build - Compile TypeScript to JavaScript in build/ directory
npm run dev - Run server in development mode with tsx
npm run watch - Run server in watch mode (auto-restart on changes)
npm start - Run the compiled server from build/index.js

Testing

node test-connection.js - Test Billy API connection and verify credentials
Set BILLY_ACCESS_TOKEN environment variable before running tests

Environment Setup

Requires Node.js 18+
Set BILLY_ACCESS_TOKEN environment variable with your Billy API access token
Run npm install to install dependencies

Architecture

This is a Model Context Protocol (MCP) server that provides Claude with tools to interact with Billy's accounting API. The architecture consists of:

Core Components

BillyClient Class (src/index.html:18-124)

Handles all Billy API communication
Manages authentication via X-Access-Token header
Provides methods for contacts, invoices, products, payments, bills, and accounts
Base URL: https://api.billysbilling.com/v2

MCP Server (src/index.html:126-516)

Implements MCP protocol using @modelcontextprotocol/sdk
Provides 13 tools for Billy API operations
Uses stdio transport for communication
Lazy-initializes Billy client on first tool call

Key Design Patterns

API Request Pattern

All API calls go through BillyClient.request() method
Consistent error handling with axios error transformation
Query parameters handled via URLSearchParams

MCP Tool Structure

Each tool has detailed JSON schema for input validation
Tools return JSON responses wrapped in MCP text content
Error responses include isError: true flag

Billy API Integration

Authentication

Uses access token authentication (X-Access-Token header)
Token set via BILLY_ACCESS_TOKEN environment variable
No OAuth support (Billy limitation)

Read the full file on GitHub · 96 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

3d ago First seen · 96 lines · 785 tokens per session scan A 40209745a7b5

Subscribe to this mod's changes

billy-mcp-server CLAUDE.md is an instructions file published in the GitHub repository markhm/billy-mcp-server (2 stars, last pushed 1y ago), licensed MIT. It adds 785 tokens to every session, about $0.0039 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

vscode buildNext.instructions.md

Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).

microsoft/vscode · 6,785 tokens

billy-mcp-server CLAUDE.md