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Volley

Volley

A good sequence diagram can solve almost any communication problem in engineering. Volley lets your agent write them as plain text, with the real request and response payloads on every arrow. It checks its own syntax with line and column errors, renders SVG, and saves diagrams and collections to your Volley account. You can also build diagrams from webhook inboxes and customer recording links, and diff a recording against the expected sequence.

Developer Tools

sequence diagrams, api, webhooks, documentation, debugging, diagrams

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https://volley.sh

https://volley.sh/docs/mcp

https://volley.sh/mcp

API key

A good sequence diagram can solve almost any communication problem in engineering. Volley is a plain-text sequence diagram tool where every arrow can carry its request and response: JSON bodies, form fields, headers and query strings.

This server lets your agent write a diagram from your codebase or API docs, check it, render it and save it to your Volley account with a short link and a README embed. Errors come back with a line and column, so the agent fixes its own mistakes.

What else Volley does

• Payloads on every arrow, shown inline or in a tray.
• Webhook inboxes: point Stripe, GitHub or anything else at one and turn the captured requests into a diagram.
• Recording links: customers get clear steps for recording a HAR file, cookies and tokens are stripped in their browser, and you get back a diagram with the failed requests marked.
• Drift check: diff a recording against the sequence you expected.

Connect

Create an API key at volley.sh under Account, then API keys.

Claude Code:

claude mcp add --transport http volley https://volley.sh/mcp \
  --header "Authorization: Bearer $VOLLEY_KEY"

Cursor and other clients with a JSON config:

{
  "mcpServers": {
    "volley": {
      "url": "https://volley.sh/mcp",
      "headers": { "Authorization": "Bearer volley_..." }
    }
  }
}

Tools

Tool	What it does
check_diagram	Errors and warnings with line and column
describe_diagram	The diagram as Markdown, with every payload
render_svg	SVG in light or dark
verify_diagram	Diff a HAR recording against the diagram
list_diagrams, get_diagram, save_diagram	Read and save diagrams in your account
list_collections, get_collection, save_collection, add_to_collection	Group diagrams into collections (saving is Pro)

Try it

Read our checkout code and draw the Stripe Checkout flow as a Volley diagram with the request and response on each call. Check it, then save it.

Plans

The editor is free with no account. The free plan includes 200 MCP calls a month; Pro is $9/month with 20,000 calls, private diagrams and version history.

Support: support@volley.sh