SignatureAPI
Mint Starter Kit

Develop with Agents

Agent Skills and Plugin

Install the SignatureAPI skills in your coding agent, on their own or as a plugin that also configures the hosted MCP server.

SignatureAPI publishes two Agent Skills for coding agents: one that builds an e-signature integration and one that diagnoses an integration that misbehaves. They are open source at github.com/signatureapi/skills and install into Claude Code, Codex, Cursor, Gemini CLI, Copilot, and every other agent that reads SKILL.md files.

The skills are for developers writing code that calls SignatureAPI. The code they help you write calls the REST API. The MCP server and the scripts bundled with the skills are the agent’s own tools for inspecting and proving the flow while it works, never a runtime dependency of your application.

Fastest path

Paste this into your agent and let it install the right thing for itself:

Set up SignatureAPI for me. Read https://signatureapi.com/docs/ai-toolkit/mcp/connecting-clients.md
and follow the section for the agent you are running in. If I am working on a codebase, install the
SignatureAPI plugin (skills plus MCP server) rather than the MCP server alone. Ask me before opening
a browser for sign-in, and never print tokens or keys. When you are done, prove it works by listing
my 5 most recent test-mode envelopes, then tell me what you changed and how to undo it.

The two skills

signatureapi-integrate

Use it when adding electronic signatures to an application, sending a document for signature, building or changing a signing flow, or wiring up webhooks. The agent reads the skill when the task matches, and the skill steers it away from guesses based on other e-signature APIs.

It ships scripts for the parts an agent should not improvise:

  • Query the published OpenAPI spec for field names, enum values, and event types instead of reading a long docs page.
  • Mint a test document and create a test-mode envelope.
  • Receive webhooks locally or watch for events while the flow runs.
  • Walk a real browser through the signing ceremony.
  • Check the local setup before starting.

It works in test mode only. A live key is refused, and no flag bypasses this. Test-mode envelopes are free, watermarked, not legally binding, and send no email to recipients.

signatureapi-diagnose

Use it when an envelope is stuck in processing, a webhook never arrived, a recipient never got the signing email, a deliverable is missing after completion, or envelope creation returns a validation error. One script fetches everything relevant for an envelope and returns a verdict.

It is read-only by construction. Every script issues GET requests only, and the skill restricts the agent to read-only tools. It runs against a test or a live key and reports which mode it resolved, so diagnosing a production envelope during an incident is safe.

What the skills contain

The skills inline concepts and gotchas only. Field names, enum values, event types, and limits are read from the OpenAPI spec on demand, and a CI test in the repository fails whenever an identifier a skill mentions stops existing in the spec. The spec always wins over the skill text.

Install

There are two install paths. They carry identical skill content and differ in one thing: whether the hosted MCP server is configured at the same time.

Skills only

Works in Claude Code, Codex, Cursor, Copilot, Amp, Antigravity, and every other agent the skills CLI supports. Installs the two skills and nothing else.

npx skills add signatureapi/skills

Update later with npx skills update.

Plugin: skills plus MCP server

The plugin installs the same two skills and configures the hosted MCP server in one step. Skills and server install and uninstall together; there is no flag to take one without the other.

/plugin marketplace add signatureapi/skills
/plugin install signatureapi@signatureapi

The server is configured but unauthenticated until first use. When Claude Code reports Needs authentication, run /mcp and complete the sign-in flow.

Claude Code turns auto-update off for third-party marketplaces. To receive updates, run /plugin, open Marketplaces, select signatureapi, and choose Enable auto-update. The plugin is versioned by commit, so every change we publish is a new version. To update by hand instead:

/plugin marketplace update signatureapi
/plugin update signatureapi@signatureapi

Requirements

  • A SignatureAPI key in the SIGNATUREAPI_KEY environment variable. The scripts read it from the environment only and never accept it as a command-line argument, since arguments end up in shell history and process listings.
  • Node.js 22 or later.

Machine-readable discovery

Agents that discover skills on their own can start at signatureapi.com/AGENTS.md, which routes to the right surface for each task. The skills are also served from the /.well-known/agent-skills discovery endpoint, so npx skills add https://signatureapi.com works as well as the repository form.

Contributing

Issues and pull requests are welcome at github.com/signatureapi/skills.