pdfcraft/crates/automation

printcraft-automation

Agent control for PrintCraft: a headless tool table over the engine, and an opt-in MCP server.

• Layer: L7 (architecture §13), but headless. It depends on engine, render and organize, never on a UI toolkit.
• Status: 20 tools covering inspection, rendering, text, page edits, metadata, undo/redo, save, combine, extract and split. Planned next: the UI control channel (ui.*, M3.9), tools for comments, forms and bookmarks as those features land, and MCP resources for page images.

API

let mut a = Automation::new().with_root("/work")?;      // optional: confine all paths
let doc = a.call("doc_open", &json!({ "path": "in.pdf" }))?;   // Vec<Content>
tools() -> Vec<ToolDef>                                  // name, title, description, input_schema, read_only, destructive, command
mcp::McpServer::new(a).serve(stdin, stdout)?             // newline-delimited JSON-RPC 2.0

Content is Json(Value) or Png { data, width, height }. Errors are UnknownTool, InvalidArgs (the call didn't match the schema) or Failed (a readable message for the agent).

Conventions

• Tool names are snake_case (page_rotate): MCP clients reject dots. ToolDef::command links a tool to the registry id it automates (page.rotate), and command_list reports the link.
• Pages and positions are 1-based. Rectangles are PDF points with the origin at the top-left of the displayed page.
• Unknown arguments are rejected, so typos fail loudly.
• Tools that change a document return its summary (doc, pages, dirty, undo, redo, …).
• doc_close refuses to drop unsaved changes unless discard_changes: true. doc_save writes atomically, incrementally in place, and in full for a new path.
• With a root set, every read and write path must resolve inside it (symlinks and .. included).

MCP server

Opt-in only. Nothing starts it automatically, and it opens no port. It runs while printcraft-cli mcp [--root DIR] runs, normally launched by an agent from its MCP configuration. It stops when stdin closes. The CLI's mcp Cargo feature (on by default) compiles it out entirely when disabled.

Implemented: initialize (protocol 2025-06-18, 2025-03-26, 2024-11-05), ping, tools/list (with readOnlyHint/destructiveHint annotations) and tools/call (JSON results also returned as structuredContent; images as image/png). Tool failures come back as isError: true results, so the agent can read and recover from them.

Adding a tool

1. Add the engine capability first, with its tests (the tool is a thin adapter).
2. Add a ToolDef in src/tools.rs: a precise description, the schema, ro()/destructive(), and cmd() if a registry command exists.
3. Handle it in Automation::call, validating pages and positions with the existing helpers.
4. Add an end-to-end test in tests/automation.rs. tool_table_is_well_formed checks names, schemas and command links.