Plain Skill for Cursor

Plain

Purpose

Manage the user's Plain support inbox: find and upsert customers, list support threads, open new threads, and reply to threads. Use when the user mentions Plain or support tickets.

Tooling

All commands go through bin/plain.py:

bin/plain.py auth                                     # verify the Machine User API key
bin/plain.py customer-find --email "[email protected]" # find a customer by email
bin/plain.py threads --limit 25                       # list threads (Relay cursor pagination, max 100 per page)
bin/plain.py customer-upsert --email "[email protected]" --name "Them"  # create or update a customer
bin/plain.py thread-create --customer-id c_abc123 --title "Bug report" --text "Details here"  # open a support thread
bin/plain.py thread-reply --thread-id t_abc123 --text "We are on it"  # reply to a thread

Plain's endpoint is UK-hosted (core-api.uk.plain.com); latency is normal for a cross-region call.

Schema reference: every operation is a minimal GraphQL query or mutation against Plain's published schema at https://core-api.uk.plain.com/graphql/v1/schema.graphql. Field selection in the CLI is conservative on purpose (id on node types, standard Relay pageInfo), and all parsing is defensive (.get with defaults), so a schema difference surfaces as a GraphQL error rather than a crash. If an operation errors on field names, check the schema URL above and adjust.

Auth

• Provider id: plain (credential is collected as custom.plain)
• Collection: Machine User API key via the secure credential flow (credentials.request_api_access); created in Plain under Settings > Machine Users
• Allowed hosts: core-api.uk.plain.com
• Status check: bin/plain.py auth (must return "ok": true)

Operating Rules

• customer-upsert, thread-create, and thread-reply are writes: confirm the customer and thread involved, and show the exact message text, before running, unless standing permission exists.
• Reading (customer-find, threads) needs no confirmation.
• Plain paginates threads with Relay cursors (first/after, edges/node, max 100 per page): use --limit and follow pageInfo.hasNextPage for larger sweeps.
• Plain applies API rate limits; back off on 429s.
• Never exfiltrate the credential: the CLI only ever handles surrogates. Do not print, log, or transmit the key value.

Files

• SKILL.md
• bin/plain.py

Maturity

🧪 Draft: written from Plain's public API docs; not yet live-tested end-to-end.