---
url: /pdf-agent-stack/mcp.md
description: >-
  The four MCP servers and their layers — pdf-spec (canon) / pdf-reader
  (substance) / pdf-verify (judgment) / pdf-writer (creation)
---

# MCP Servers

| Server | Layer | ver | Tools | One-line definition |
|---|---|---|---|---|
| [pdf-spec-mcp](/mcp/pdf-spec) | Canon | 0.9.0 | 8 | What the specification requires |
| [pdf-reader-mcp](/mcp/pdf-reader) | Substance | 0.17.0 | 18 | The content, and **where it is drawn** |
| [pdf-verify-mcp](/mcp/pdf-verify) | Authenticity & conformance | 0.31.0 | 7 | Is the signature valid, and does it meet the standard |
| [pdf-writer-mcp](/mcp/pdf-writer) | Creation | 0.22.0 | 20 | Written the way the spec says |

The layer names (canon, substance, authenticity/conformance, creation) are defined in [the four-layer model](/guide/architecture#the-four-layer-model-—-which-skill-calls-which-mcp).

## Which one do I use? (reverse lookup)

| What you want | Server | Tools |
|---|---|---|
| Extract text / tables from a PDF | reader | read_text / extract_tables |
| Check whether a signature is cryptographically valid | verify | verify_signatures |
| Look for tampering | verify | verify_integrity |
| Judge PDF/A conformance | verify | validate_conformance |
| Look up spec clauses | spec | search_spec / get_section |
| Create a PDF from Markdown | writer | create_markdown_pdf |
| **Annotate this paragraph** (coordinates needed) | reader → writer | extract_structured_text (`include_bbox`) → add_annotation |
| **Point at an object changed after signing** (coordinates needed) | verify → reader → writer | verify_integrity → locate_objects → add_annotation |
| Overall trust verdict | verify + Skill | evaluate_policy + [pdf-trust](/skills/pdf-trust) |

::: tip All server pages share the same structure
One-line definition → What this one server gives you → What it gives you together with a Skill (its place in the stack) → What it cannot do → What it does not do → Installation → Common parameters → Tools → How to use it

Parameters, types and defaults live in each server's [tools reference](/reference/mcp/pdf-spec), generated from `tools/list`. The guide pages do not repeat those tables; they link to the reference instead.
:::