# Reading a document in parts Walking a large document part by part: the range a conversion reports, the headers carrying it, and `part=N`. A conversion self-describes its part range, so a large document can be walked part by part without converting it again. The two headers are on every response; the same pair sits in the JSON body under `parts`. | Field | Meaning | | ---------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `parts.count` / `X-MDAPI-Parts` | How many parts the document has - the range `part` accepts | | `parts.unit` / `X-MDAPI-Part-Unit` | What a part is: `page`, `slide`, `sheet`, `chapter`, or `a4` (one A4 sheet of text) | | `parts.listed` | A book's inventory, in document order. It can name more entries than `parts.count`: a clamped book keeps its whole listing, so the tail is listed but not addressable | | `parts.truncated` | The document was cut while it was built (archive entry cap or output budget). Present only when true | | `parts.names` / `parts.sizes` | `result=meta` only: the title of each part, and its size in chars, tokens and bytes - what fits a context window, reported before the content itself is fetched | `result=meta` reports the same range before anything is converted - ask for it first when the size of the answer matters more than the answer. The unit is decided by the format, not chosen by the caller: | Unit | Formats | What one unit is | | --------- | ------------------------------------------------------------------------------------------------------------------------------ | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `page` | PDF | One page. Every page carries its own heading, so a page range is a part range | | `slide` | Presentations (PPTX, PPT, POT, PPS, ODP) | One slide, in document order | | `sheet` | Spreadsheets (XLSX, XLS, XLSM, XLSB, ODS, ET, Numbers, DTA) | One sheet, carrying its own name as the heading | | `chapter` | Books - EPUB and the archives (ZIP, TAR, 7z, and the compression family once it is unwrapped) | One entry of the book. `.tar.zst`, `.tar.xz`, `.tar.bz2` and `.tar.gz` expand to the same book as a plain `.zip`, and so does a compressed file opened from a data URI - one entry, one unit, whatever the transport | | `a4` | Anything else with a text layer and no natural boundary - DOCX, DOC, ODT, RTF, text and code, CSV/TSV, JSON/YAML, HTML, images | One A4 sheet of text: 2500 characters, the density of a page at 12pt. It is also the fallback when a format has a boundary of its kind but its markdown carries none, so `parts.unit` is always the truth to read | A part carries the document's front matter in front of it - the title, the metadata block and a book's `## Contents` listing, everything before the first unit - so a single part is readable on its own, without a second request for the context. This is what `parts.sizes` measures: each size is what `part=N` alone returns, front matter included, so the sizes add up to a little more than the whole document rather than exactly to it. A part of an A4 document has no front matter to carry and gets a generated `## Part N` heading instead. ## Links - **About service:** https://mdapi.io/about - **API documentation and conversion:** https://mdapi.io - **MCP server manifest:** https://mdapi.io/mcp - **Health check:** https://mdapi.io/health - **Documentation index:** https://mdapi.io/llms.txt - **Full API documentation:** https://mdapi.io/llms-full.txt - **AI discovery:** https://mdapi.io/.well-known/ai-discovery.json or https://mdapi.io/ai-discovery.json - **AI Agent discovery:** https://mdapi.io/.well-known/agent.json or https://mdapi.io/agent.json - **A2A Agent card:** https://mdapi.io/.well-known/agent-card.json or https://mdapi.io/agent-card.json - **ACP manifest:** https://mdapi.io/.well-known/acp.json or https://mdapi.io/acp.json - **x402 payment manifest:** https://mdapi.io/.well-known/x402.json or https://mdapi.io/x402.json - **OpenAPI specification (JSON):** https://mdapi.io/.well-known/openapi.json or https://mdapi.io/openapi.json - **OpenAPI specification (YAML):** https://mdapi.io/.well-known/openapi.yaml or https://mdapi.io/openapi.yaml - **MAPI specification:** https://mdapi.io/.well-known/mapi.md or https://mdapi.io/mapi.md - **Skill specification:** https://mdapi.io/.well-known/skill.md or https://mdapi.io/skill.md - **Agent Plugins manifest:** https://mdapi.io/.well-known/plugin/plugin.json or https://mdapi.io/.well-known/plugin.json - **Agent Plugins MCP config:** https://mdapi.io/.well-known/plugin/mcp.json - **Agent Plugins conversion skill:** https://mdapi.io/.well-known/plugin/skills/mdapi-conversion/SKILL.md - **API documentation pages:** https://mdapi.io/docs ## External Links - **github.com** https://github.com/mdapiio/mdapi.io - **skills.sh** https://www.skills.sh/mdapiio/mdapi.io - **skillsmp.com** https://skillsmp.com/creators/mdapiio/mdapi.io - **clawhub.ai** https://clawhub.ai/mdapiio - **x.com** https://x.com/mdapiio ## Disclaimer **The service is provided "AS IS".** > mdapi.io is an edge-native service-transport primitive for AI, autonomous-agents, and the Web4 ecosystem.