# render_diagram

> Page: https://docs.plotwork.dev/mcp/tools/render-diagram. Index of every page: https://docs.plotwork.dev/llms.txt

Render valid source to a self-contained, accessible SVG in the light or dark theme, with its pixel size and quality warnings. It is a single tool of the MCP server and the HTTP API, with the title "Render diagram".

## TL;DR

| Question | Answer |
|---|---|
| What is it? | A single tool: it does one thing. |
| What does it do? | Render valid source to a self-contained, accessible SVG in the light or dark theme, with its pixel size and quality warnings. |
| How do I call it over HTTP? | [`POST /v1/diagrams/render`](https://docs.plotwork.dev/api/post-v1-diagrams-render.md) |
| Does it change anything? | No. It is read-only and idempotent, and it talks to nothing outside itself. It saves no file and returns its answer as data. |
| Which bounds apply? | None beyond the limits of each argument, which are in the schema below. |
| Where do I read its schema as data? | An MCP client gets the name, description, and JSON Schema of every tool from `tools/list`. |

## What it does

Render valid source to a self-contained, accessible SVG in the light or dark theme, with its pixel size and quality warnings. Source with errors fails with its diagnostics. Set embedSource true to save the SVG in a repository, so read_diagram can give the source back. Prefer draw_diagram, which validates, outlines, and renders in one call.

## Arguments

| Field | Type | Required | Description |
|---|---|---|---|
| `source` | `string` | yes | Diagram source; the first line is the header, such as flow "Title" (draw_diagram lists every kind). at least 1 character; at most 50000 characters. |
| `theme` | `"light" \| "dark" \| "auto"` | no | Color scheme to paint with: light, dark, or auto for one picture that follows the reader's light or dark setting. default "light". |
| `idPrefix` | `string` | no | Prefix for element ids; set it when inlining several diagrams into one page. at most 32 characters; pattern `^[A-Za-z][A-Za-z0-9_-]*$`. |
| `embedSource` | `boolean` | no | Write the source into the SVG metadata so read_diagram can give it back. Set it true when you save the SVG into a repository; anyone with the file can then read the source. Default false. default false. |
| `settings` | `object` | no | The repo's plotwork.config.json, if any. Schema: https://docs.plotwork.dev/schemas/plotwork.config.json. |

## Result

| Field | Type | Required | Description |
|---|---|---|---|
| `svg` | `string` | yes | Self-contained SVG markup with an accessible title and description. |
| `theme` | `"light" \| "dark" \| "auto"` | yes | The color scheme used. |
| `size` | `Size` | yes | Natural size of a rendered diagram in px. |
| `size.width` | `integer` | yes | Width in px. minimum 1. |
| `size.height` | `integer` | yes | Height in px. minimum 1. |
| `warnings` | `Diagnostic[]` | yes |  |
| `warnings[].code` | `"E100" \| "E101" \| "E110" \| "E111" \| "E120" \| "E121" \| "E122" \| "E123" \| "E124" \| "E125" \| "E130" \| "E131" \| "E132" \| "E133" \| "E134" \| "E135" \| "E136" \| "E137" \| "E138" \| "E139" \| "E140" \| "W200" \| "W201" \| "W202" \| "W203" \| "W204" \| "W205" \| "W206" \| "W207" \| "W500" \| "M100" \| "M101" \| "M102" \| "M103" \| "M104" \| "M110" \| "M200" \| "M201" \| "M202" \| "M203" \| "M204" \| "M205" \| "M206" \| "M207" \| "M208" \| "M209" \| "M210" \| "M211" \| "M212" \| "M213" \| "M214" \| "M215" \| "M216" \| "M217" \| "M218" \| "E300" \| "E301" \| "E302" \| "E303" \| "E304" \| "W300" \| "W301" \| "W302" \| "W303" \| "M120" \| "M220" \| "M221" \| "M222" \| "E340" \| "E341" \| "E342" \| "E343" \| "E344" \| "E345" \| "W320" \| "W321" \| "W322" \| "W323" \| "M240" \| "M241" \| "M242" \| "E360" \| "E361" \| "E362" \| "E363" \| "E364" \| "E365" \| "E366" \| "E367" \| "W330" \| "W331" \| "W332" \| "W333" \| "W334" \| "M250" \| "M251" \| "E400" \| "E401" \| "E402" \| "E403" \| "W350" \| "W351" \| "W352" \| "W353" \| "M270" \| "M271" \| "E420" \| "E421" \| "E422" \| "E423" \| "E424" \| "W360" \| "W361" \| "W362" \| "W363" \| "W364" \| "M180" \| "M280" \| "M281" \| "M282" \| "E320" \| "E321" \| "E322" \| "E323" \| "E324" \| "E325" \| "E326" \| "E327" \| "E328" \| "E329" \| "E330" \| "W310" \| "W311" \| "W312" \| "W313" \| "W314" \| "M130" \| "M131" \| "M132" \| "M230" \| "M231" \| "M232" \| "M233" \| "M234" \| "M235" \| "M236" \| "M237" \| "M238" \| "E380" \| "E381" \| "E382" \| "E383" \| "W340" \| "W341" \| "W342" \| "W343" \| "M260" \| "I100" \| "I101" \| "I102" \| "I103" \| "I104" \| "I105" \| "I200" \| "I201" \| "I202" \| "I203" \| "I204" \| "I206" \| "R100" \| "R101" \| "R200" \| "R201" \| "R202" \| "R203" \| "R204" \| "R205" \| "R206" \| "R207" \| "S100" \| "S200" \| "S101" \| "S102" \| "S103" \| "S104" \| "S201" \| "S202" \| "S203"` | yes | Stable code to branch on; E-codes are errors, W-codes are warnings. |
| `warnings[].severity` | `"error" \| "warning"` | yes | Errors stop rendering; warnings never do. |
| `warnings[].message` | `string` | yes | What is wrong, in one sentence. |
| `warnings[].line` | `integer` | yes | 1-based line in the submitted source. minimum 1. |
| `warnings[].column` | `integer` | yes | 1-based column in that line. minimum 1. |
| `warnings[].length` | `integer` | yes | Number of characters the problem covers. minimum 1. |
| `warnings[].hint` | `string \| null` | yes | A concrete suggestion for fixing it, or null. |

## Behavior hints

| Hint | Value |
|---|---|
| `readOnlyHint` | true |
| `destructiveHint` | false |
| `idempotentHint` | true |
| `openWorldHint` | false |

## See also

| Doc | Why |
|---|---|
| [Tool reference](https://docs.plotwork.dev/mcp/tools.md) | Every tool, with the workflows first |
| [`POST /v1/diagrams/render`](https://docs.plotwork.dev/api/post-v1-diagrams-render.md) | The same operation over HTTP |
| [Language reference](https://docs.plotwork.dev/reference/language.md) | What the diagram source may contain |
| [Writing diagrams with an agent](https://docs.plotwork.dev/mcp/agent-loop.md) | The loop in practice |