Custom Plugin Development

Custom Plugins for
Claude Cowork

We build Cowork plugins tailored to your specific workflows. Skills, commands, connectors, agents, and hooks designed for how your team actually works.

One-time setup. Ongoing value without ongoing consulting fees.

Why Generic Plugins Fall Short

Anthropic ships 11 official plugins covering broad roles like Sales, Marketing, and Productivity. They're solid starting points. But your business doesn't run on generic processes.

A real estate brokerage needs a plugin that follows their specific CMA template, writes in their brand voice, and pulls comps from their MLS system. A law firm needs contract review skills trained on their clause library, not generic legal templates. An accounting firm needs reconciliation workflows that match their chart of accounts, not a one-size-fits-all ledger format.

Generic Plugin

Produces output that's close but never quite right. Your team spends 20 minutes editing every deliverable to match your standards, templates, and terminology. The time savings erode fast.

Custom Plugin

Produces work that matches how your team already operates. Your CMA template. Your clause library. Your chart of accounts. Your brand voice. Output that needs minimal revision because it was built around your process from the start.

How a Cowork Plugin Is Structured

Every plugin is a folder of markdown and JSON files. No compiled code, no infrastructure to maintain, no build steps. Here's what goes inside.

plugin-name/ .claude-plugin/plugin.json # Manifest (metadata) .mcp.json # Tool connections (MCP servers) commands/ # Slash commands (explicit user actions) skills/ # Domain knowledge (auto-invoked) agents/ # Specialized sub-agents hooks/ # Event handlers

Skills

Domain expertise that Claude draws on automatically when relevant. Each skill is a SKILL.md file with YAML frontmatter defining when it should activate. Your CMA formatting rules, your contract review checklist, your brand voice guidelines. Claude applies them without being asked. Full skills guide.

Commands

Explicit actions your team triggers with a slash. Type /sales:call-prep and Claude pulls the prospect's data from your CRM, checks recent email threads, and generates a briefing doc. Type /finance:reconciliation and it walks through your monthly close checklist step by step.

Connectors

MCP server configurations in a single .mcp.json file. These wire Claude to your external tools: HubSpot, Salesforce, QuickBooks, Google Drive, Slack, Jira, and dozens more. Each connection uses OAuth with scoped permissions. Full connectors guide.

Agents

Specialized sub-agents for specific tasks. Claude invokes them automatically when a task matches their scope. For example, a drafting agent that writes in your firm's style, or a review agent that checks output against your quality standards before delivering it.

Hooks

Event handlers that fire before or after specific actions. JSON configuration files with matchers and actions. Use PreToolUse hooks to add guardrails before Claude sends an email. Use PostToolUse hooks to log every CRM update. Use SessionStart hooks to load context at the beginning of every conversation.

Custom Plugins We Build

Every industry has workflows that don't fit neatly into a generic template. Here's what custom plugins look like in practice.

Real Estate

  • • Weekly market report skill with your brokerage's data sources
  • • CMA template skill that follows your firm's exact format
  • • Listing description generator with brand voice enforcement
  • • Lead follow-up automation connected to your CRM

Real estate plugins

Legal

  • • Contract review with your firm's clause library
  • • NDA triage workflow that flags non-standard terms
  • • Discovery document organization by matter type
  • • Client intake processing connected to your practice management system

Legal plugins

Finance and Accounting

  • • Journal entry skills tied to your specific chart of accounts
  • • Reconciliation workflows for your banks and platforms
  • • Variance analysis with custom thresholds by account
  • • Monthly close checklist automation

Finance plugins

Marketing

  • • Brand voice enforcement skill across all content types
  • • Campaign brief generator connected to HubSpot
  • • SEO content workflow with Ahrefs data integration
  • • Social media calendar builder with platform-specific formatting

Marketing plugins

How a Custom Plugin Engagement Works

Building a plugin that actually fits your workflows takes back-and-forth with your team. Here's how we do it.

1

Discovery Call

We start with a 15-minute call to understand your workflows, the tools you use daily, and where you're losing time. This tells us whether a custom plugin is the right fit or if configuration of existing plugins would solve the problem.

2

Workflow Mapping

We map each task to the right plugin component. Repeatable processes become skills. User-triggered actions become commands. Tool integrations become connector configurations. Guardrails and logging become hooks. This mapping is the blueprint for your plugin.

3

Build

We write every component: skill files with YAML frontmatter, command definitions, MCP server configs, agent specs, and hook handlers. Most plugins take 1-2 weeks to build. Everything is file-based, so you can read and understand every piece of it.

4

Test and Iterate

Your team runs the plugin against real work and provides feedback. We tune the skills, adjust command prompts, and refine output quality until the deliverables meet your standards.

5

Deploy and Connect

We install the plugin, wire up all connector OAuth flows, configure permissions, and verify everything works end to end. For enterprise teams, we add the plugin to your organization marketplace with the right installation preferences.

6

Train Your Team

We run a training session covering every command, when skills activate, and how to customize the plugin yourself. Your team leaves the session able to use every feature independently.

7

Maintain

Cowork is still evolving. Anthropic ships platform updates regularly, and those updates sometimes change how plugins work. We keep your plugin compatible so your team never wakes up to a broken workflow.

Why Not Build It Yourself?

You could. The plugin system is open and file-based. But there are reasons most teams hire us instead.

MCP Expertise

Configuring MCP servers, scoping permissions, and handling OAuth flows across multiple platforms takes specific knowledge. We've done it dozens of times across HubSpot, Salesforce, QuickBooks, and more.

Skill Crafting

The difference between mediocre and excellent plugin output comes down to how well the skills and global instructions are written. We've iterated on enough plugins to know what works and what doesn't.

Time

Learning the plugin system from scratch takes weeks of experimentation. Your team has work to do. We handle the setup so you can go straight to the value.

Frequently Asked Questions

How long does it take to build a custom plugin?
Most plugins take 1-2 weeks from kickoff to deployment. That includes discovery, workflow mapping, building all components, testing with your team, and installation. Plugins with extensive connector configurations or large skill libraries may take closer to 3 weeks.
Do I need technical skills to use a custom plugin?
No. Once installed, a custom plugin works like any other Cowork plugin. You interact with Claude in natural language, and the plugin's skills, commands, and connectors operate behind the scenes. We also train your team on every component during deployment.
Can you fork an official Anthropic plugin instead of building from scratch?
Yes, and it's often the fastest path. We take the closest official plugin, keep the parts that work for your use case, replace what doesn't fit, and layer your industry-specific skills and connectors on top. This gives you a head start without sacrificing customization. Read the full plugins guide.
What happens when Anthropic updates Cowork and my plugin breaks?
Cowork is still in research preview, so platform changes happen regularly. We offer ongoing maintenance to keep your plugins compatible. When Anthropic changes something that affects your plugin, we update the affected components so your workflows keep running without interruption.
Can a single plugin connect to multiple external tools?
Yes. A plugin's .mcp.json file can define connections to as many MCP servers as you need. A single sales plugin could connect to HubSpot for CRM data, Gmail for email drafting, and Google Sheets for pipeline tracking. Each connection uses scoped OAuth permissions. Read the connectors guide.

Ready to Build Your Custom Plugin?

Book a free 15-minute call. We'll walk through your workflows, identify which tasks fit the plugin model, and outline what a custom build would look like for your team.

Book a Free 15-Minute Call

No commitment. No sales pitch. Just a straight look at what we can build for you.