Live 78 Actions

Harvest MCP Server
for AI Agents

Q: What AI frameworks and AI clients does the StackOne Harvest MCP server support?

The StackOne Harvest MCP server supports both. MCP clients (paste-and-go apps): Claude Desktop, Claude Code, Cursor, VS Code, Goose. Agent frameworks (code SDKs you build with): OpenAI Agents SDK, Anthropic, Vercel AI, Google ADK, CrewAI, Pydantic AI, LangChain, LangGraph, Azure AI Foundry.

Connect your AI agent to StackOne's Harvest MCP server and give it 78 MCP tools out of the box. Auth, tool execution, and security all managed.

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Harvest MCP Server

Built by

StackOne

Coverage

78 Agent Actions

Create, read, update, and delete across Harvest — and extend your agent's capabilities with custom actions.

MCP Actions → Build Actions →

Authentication

Agent Tool Authentication

Per-user OAuth in one call. Your Harvest MCP server gets session-scoped tokens with zero credentials stored on your infra.

Agent Auth →

Security

Agent Protection

Every Harvest tool response scanned for prompt injection in milliseconds — 88.7% accuracy, all running on CPU.

Prompt Injection Defense →

Performance

Max Agent Context. Min Cost.

Free up to 96% of your agent's context window to enhance reasoning and reduce cost, on every Harvest call.

Tools Discovery →

What is the Harvest MCP Server?

A Harvest MCP server lets AI agents read and write Harvest data through the Model Context Protocol — Anthropic's open standard for connecting LLMs to external tools. StackOne's Harvest MCP server ships with 78 pre-built actions, fully extensible via the Connector Builder — plus managed authentication, prompt injection defense, observability, and agent execution runtime. Connect it from MCP clients like Claude Desktop, Claude Code, Cursor, Goose, and VS Code, or from agent frameworks like OpenAI Agents SDK, LangChain, and Vercel AI SDK.

All Harvest MCP Tools

Every action from Harvest's API, ready for your agent. Create, read, update, and delete — scoped to exactly what you need.

Clients

Create Client
Create a new client.
List Clients
List all clients in the Harvest account.
Get Client
Retrieve a single client by ID.
Update Client
Update an existing client.
Delete Client
Delete a client.

Contacts

Create Contact
Create a new contact.
List Contacts
List all contacts in the Harvest account.
Get Contact
Retrieve a single contact by ID.
Update Contact
Update an existing contact.
Delete Contact
Delete a contact.

Estimates

Create Estimate
Create a new estimate.
List Estimates
List all estimates in the Harvest account.
Get Estimate
Retrieve a single estimate by ID.
Update Estimate
Update an existing estimate.
Delete Estimate
Delete an estimate.

Expenses

Create Expense
Create a new expense, optionally with a receipt file attached.
List Expenses
List all expenses in the Harvest account.
Get Expense
Retrieve a single expense by ID.
Update Expense
Update an existing expense, optionally replacing or deleting its receipt.
Delete Expense
Delete an expense.

Invoice Messages

Create Invoice Message
Create and send a new invoice message.
List Invoice Messages
List all messages associated with a specific invoice.
Delete Invoice Message
Delete an invoice message.

Invoice Payments

Create Invoice Payment
Record a new payment against an invoice.
List Invoice Payments
List all payments recorded against an invoice.
Delete Invoice Payment
Delete an invoice payment.

Invoices

List Invoices
List all invoices in the Harvest account.
Get Invoice
Retrieve a single invoice by ID.
Update Invoice
Update an existing invoice. Preview — payment_options values (ach, credit_card) require the corresponding payment gateway integration (Stripe / ACH) to be activated in the Harvest workspace under Settings > Integrations; without it, Harvest rejects the update with 422 "Enabled payment options is invalid". PayPal works on accounts where the PayPal integration is active.
Delete Invoice
Delete an invoice.

Projects

Create Project
Create a new project.
List Projects
List all projects in the Harvest account.
Get Project
Retrieve a single project by ID.
Update Project
Update an existing project.
Delete Project
Delete a project.

Roles

List Roles
List all roles in the Harvest account.
Get Role
Retrieve a single role by ID.

Tasks

Create Task
Create a new task.
List Tasks
List all tasks in the Harvest account.
Get Task
Retrieve a single task by ID.
Update Task
Update an existing task.
Delete Task
Delete a task.

Time Entrys

Get Time Entry
Retrieve a single time entry by ID.
Update Time Entry
Update an existing time entry.
Delete Time Entry
Delete a time entry.

Users

Create User
Create a new user.
List Users
List all users in the Harvest account.
Get User
Retrieve a single user by ID.
Update User
Update an existing user.
Delete User
Delete a user.

Other (28)

Create Estimate Message
Create a new message for an estimate.
Create Free-Form Invoice
Create a new free-form invoice. Preview — payment_options values (ach, credit_card) require the corresponding payment gateway integration (Stripe / ACH) to be activated in the Harvest workspace under Settings > Integrations; without it, Harvest rejects the call with 422 "Enabled payment options is invalid". PayPal works on accounts where the PayPal integration is active.
Create Invoice From Tracked Time And Expenses
Create a new invoice populated from tracked time and expenses. Preview — payment_options values (ach, credit_card) require the corresponding payment gateway integration (Stripe / ACH) to be activated in the Harvest workspace under Settings > Integrations; without it, Harvest rejects the call with 422 "Enabled payment options is invalid". PayPal works on accounts where the PayPal integration is active.
Create Time Entry Via Duration
Create a new time entry using duration (hours).
Create Time Entry Via Start And End Time
Create a new time entry using start and end times.
Get Company
Retrieve the company for the currently authenticated user.
List Estimate Item Categories
List all estimate item categories in the Harvest account.
List Expense Categories
List all expense categories in the Harvest account.
List Invoice Item Categories
List all invoice item categories in the Harvest account.
List Team Time Report
Retrieve aggregated time totals grouped by team member for a given timeframe.
List Project Budget Report
Retrieve budget information for projects that have been assigned a budget.
List Uninvoiced Report
Retrieve uninvoiced hours and expenses for all billable projects in a timeframe.
List Task Assignments
List all task assignments across all projects in the Harvest account.
List Task Assignments For Project
List all task assignments for a specific project.
List Time Entries
List all time entries in the Harvest account.
List User Assignments
List all user assignments across all projects in the Harvest account.
List User Assignments For Project
List all user assignments for a specific project.
List User Billable Rates
List all billable rates for a specific user.
List User Cost Rates
List all cost rates for a specific user.
List User Project Assignments
List active project assignments for a specific user.
List My Project Assignments
List active project assignments for the currently authenticated user.
Get Current User
Retrieve the currently authenticated user.
Mark Estimate As Sent
Mark a draft estimate as sent.
Mark Estimate As Accepted
Mark an open estimate as accepted.
Mark Invoice As Sent
Mark a draft invoice as sent.
Mark Invoice As Closed
Mark an open invoice as closed (written off).
Restart Time Entry
Restart a stopped time entry.
Stop Time Entry
Stop a running time entry.

Harvest AI Agent Use Cases

Connect your AI agent to Harvest and help your team scale the HR operations they run by hand today.

Employee Onboarding

Use StackOne to connect your AI agent to your HRIS, identity management, and LMS to automate employee onboarding.

View

HR Policy Q&A Chatbot

Use StackOne to connect your AI agent to your HRIS, knowledge base, and messaging tools to automate HR policy Q&A.

View

Employee Offboarding

Use StackOne to connect your AI agent to your HRIS, identity management, and ITSM to automate employee offboarding and deprovisioning.

View

More HRIS & HCM use cases

Set Up Your Harvest MCP Server in Minutes

One endpoint. Any framework. Your agent is talking to Harvest in under 10 lines of code.

MCP Clients

Agent Frameworks

Claude Desktop-

JSON

Claude Desktop Docs

{
  "mcpServers": {
    "stackone": {
      "command": "npx",
      "args": [
        "-y",
        "mcp-remote@latest",
        "https://api.stackone.com/mcp?x-account-id=<account_id>",
        "--header",
        "Authorization: Basic <YOUR_BASE64_TOKEN>"
      ]
    }
  }
}

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Platform Resources

MCP Code Mode: Keeping Tool Responses Out of Agent Context

Anthropic's code_execution processes data already in context. Custom MCP code mode keeps raw tool responses in a sandbox. 14K tokens vs 500.

11 min

Comparing BM25, TF-IDF, and Hybrid Search for MCP Tool Discovery

Benchmarking BM25, TF-IDF, and hybrid search for MCP tool discovery across 916 tools. The 80/20 TF-IDF/BM25 hybrid hits 21% Top-1 accuracy in under 1ms.

10 min

Indirect Prompt Injection Defense for MCP Tools: A Technical Guide

MCP tools that read emails, CRM records, and tickets are indirect prompt injection vectors. Here's how we built a two-tier defense that scans tool results in ~11ms.

12 min

MCP vs A2A: Architecture, Security, and When to Use Each

MCP vs A2A: what each protocol standardizes, how they differ, their shared security risks including indirect prompt injection, and when to use one, both, or a hybrid architecture.

12 min

MCP vs API: What 200+ Connector Builds Taught Us

MCP wraps APIs, it doesn't replace them. After building 200+ connectors that serve both, here's when each approach wins.

14 min read

Harvest MCP Server FAQ

Does StackOne have a Harvest MCP server?

Yes. StackOne offers a hosted Harvest MCP server with 78 pre-built actions, and every action is tested and QA'd by StackOne. Connect it to Claude, Cursor, and any other MCP client, or to any agent framework through the AI Action SDK. It ships with managed agent authentication, prompt injection defense, and tool discovery with server-side execution that preserve your agent's context window and keep reasoning performance.

Harvest MCP server vs direct API integration — what's the difference?

A Harvest MCP server and direct API integration serve different use cases. Direct API integration is for software-to-software — backend code calling Harvest. A Harvest MCP server is for AI agents — MCP clients like Claude and Cursor, plus framework agents built with OpenAI, LangChain, or Vercel AI — discovering and calling Harvest at runtime. StackOne provides both.

How does Harvest authentication work for AI agents?

Harvest authentication for AI agents works through a StackOne Connect Session. Create one via the dashboard or the SDK — you get an auth link and ready-to-paste config for Claude Desktop, Cursor, and other MCP clients. Your user authenticates their own Harvest account; StackOne handles token exchange, storage, and refresh. Credentials never reach the LLM, and each user is isolated via origin_owner_id.

Are Harvest MCP tools vulnerable to prompt injection?

Yes — Harvest MCP tools can be vulnerable to indirect prompt injection. Any tool that reads user-written content — documents, messages, tickets, records, or free-text fields — is a potential vector. StackOne Defender scans every tool response before it enters the agent's context — regex patterns in ~1ms, then a MiniLM classifier in ~4ms. 88.7% accuracy, CPU-only.

What is the context bloat of a Harvest agent and how do I avoid it?

Context bloat happens when Harvest tool schemas and API responses eat your Harvest agent's memory, preventing it from reasoning effectively. A single Harvest query can return a massive JSON response, and connecting multiple tools compounds the problem. Tools Discovery and Code Mode reduce context bloat — loading only relevant tools per query and keeping raw responses out of the agent's context.

Can I limit which actions my Harvest agent can access?

Yes — you can limit which actions your Harvest agent can access directly from the StackOne dashboard. Toggle actions on or off, or restrict them to specific accounts, with no code changes to your agent. Session tokens can be scoped to exact actions so if one leaks, exposure stays contained.

Can I create custom agent actions for my Harvest MCP server?

Yes — you can create custom agent actions for your Harvest MCP server using Connector Builder. It's an integration agent your coding assistant (Claude Code, Cursor, or Copilot) can invoke to research Harvest's API, generate production-ready connector YAML, test against the live API, and validate before you ship.

When should I NOT use a Harvest MCP server?

Skip a Harvest MCP server if your integration is purely software-to-software — direct Harvest API integration is simpler when no AI agent is involved. For deterministic, compliance-critical operations (financial transactions, regulatory reporting), direct API gives you predictable behavior without agent-driven decision-making. MCP shines when AI agents need to dynamically discover and call Harvest actions at runtime.

What AI frameworks and AI clients does the StackOne Harvest MCP server support?

The StackOne Harvest MCP server supports both. MCP clients (paste-and-go apps): Claude Desktop, Claude Code, Cursor, VS Code, Goose. Agent frameworks (code SDKs you build with): OpenAI Agents SDK, Anthropic, Vercel AI, Google ADK, CrewAI, Pydantic AI, LangChain, LangGraph, Azure AI Foundry.

Put your AI agents to work

All the tools you need to build and scale AI agent integrations, with best-in-class connectivity, execution, and security.

Start Free Book Demo

Harvest MCP Serverfor AI Agents

78 Agent Actions

Agent Tool Authentication

Agent Protection

Max Agent Context. Min Cost.

What is the Harvest MCP Server?

All Harvest MCP Tools

Clients

Contacts

Estimates

Expenses

Invoice Messages

Invoice Payments

Invoices

Projects

Roles

Tasks

Time Entrys

Users

Other (28)

Harvest AI Agent Use Cases

Set Up Your Harvest MCP Server in Minutes

Check More HRIS / HCM MCP Servers

Platform Resources

MCP Code Mode: Keeping Tool Responses Out of Agent Context

Comparing BM25, TF-IDF, and Hybrid Search for MCP Tool Discovery

Indirect Prompt Injection Defense for MCP Tools: A Technical Guide

MCP vs A2A: Architecture, Security, and When to Use Each

MCP vs API: What 200+ Connector Builds Taught Us

Harvest MCP Server FAQ

Put your AI agents to work

Harvest MCP Server
for AI Agents