# edit_diagram

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

Changes diagram source with typed operations, on every kind, and checks the result. It is a workflow of the MCP server and the HTTP API, with the title "Edit diagram".

## TL;DR

| Question | Answer |
|---|---|
| What is it? | A workflow: one call does the work of several tools and returns one combined answer. |
| What does it do? | Changes diagram source with typed operations, on every kind, and checks the result. |
| What does it replace? | rewriting the source by hand and the draw_diagram check. |
| How do I call it over HTTP? | [`POST /v1/diagrams/edit`](https://docs.plotwork.dev/api/post-v1-diagrams-edit.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? | `maxEditOperations`, `maxEditTextLength`. See the bounds 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

Workflow. Changes diagram source with typed operations, on every kind, and checks the result. Each op and its fields: rename (target, to: an id everywhere it is used, or a label), set (target, or from and to for an edge, or target "header"; option, value, null removes it), add_node (id, label, type, options; into a block or after a statement; statement for a whole line), remove (target, with its block and edges), add_edge (from, to, label, arrow, options), remove_edge (from, to, label), move (target, into: a block, or null for the top level), replace_text (find, replace, all). Untouched lines keep their comments and layout. Each op reports applied, or why not with a hint, and a failed one is skipped. svg "never" (the default) lays nothing out; auto or always draws as draw_diagram does, with viewUrl and saveCommand. Replaces rewriting the source by hand and the draw_diagram check.

## Steps

| Operation | Runs | What it does |
|---|---|---|
| `parse` | only when needed | Parse the source and return its errors, without laying it out or linting it. |
| `outline` | only when needed | Describe a valid diagram as plain text. |
| `validate` | only when needed | Parse the source and lint it: every error, and the quality, icon, and group-type warnings. |
| `render` | only when needed | Lay out and paint a valid diagram in one color scheme. |

One call performs at most 4 operations.

## Example call

The arguments of the call, as JSON:

```json
{
  "source": "flow \"Login\" direction=right\n# the sign-in path\nnode user person \"User\"\nnode api service \"Auth API\"\nnode db database \"Users DB\"\nuser -> api : \"POST /login\"\napi -> db : \"look up user\"",
  "operations": [
    {
      "op": "rename",
      "target": "api",
      "to": "gateway"
    },
    {
      "op": "set",
      "target": "db",
      "option": "icon",
      "value": "simple:postgresql"
    },
    {
      "op": "add_node",
      "id": "cache",
      "type": "database",
      "label": "Session cache"
    },
    {
      "op": "add_edge",
      "from": "gateway",
      "to": "cache",
      "label": "store session"
    }
  ]
}
```

The `source` argument, written out one line at a time:

```plotwork
flow "Login" direction=right
# the sign-in path
node user person "User"
node api service "Auth API"
node db database "Users DB"
user -> api : "POST /login"
api -> db : "look up user"
```

## Prompts that lead to it

- Rename the Auth API node to gateway and add a session cache it writes to.
- Move the database into the data group and remove the old queue.

## 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. |
| `operations` | `object[]` | yes | Applied in order. |
| `operations[].op` | `"rename" \| "set" \| "add_node" \| "remove" \| "add_edge" \| "remove_edge" \| "move" \| "replace_text"` | yes |  |
| `operations[].target` | `string` | no | Id, label, table.column, or "header". at most 2000 characters. |
| `operations[].to` | `string` | no | rename: the new name. Edges: the end. at most 2000 characters. |
| `operations[].from` | `string` | no | Edges: the start. at most 2000 characters. |
| `operations[].option` | `string` | no | at most 40 characters; pattern `^[a-z][A-Za-z0-9_-]*$`. |
| `operations[].value` | `string \| null` | no | set: null removes the option. |
| `operations[].id` | `string` | no | at most 2000 characters. |
| `operations[].label` | `string` | no | add_edge on sankey: the amount. at most 2000 characters. |
| `operations[].type` | `string` | no | add_node: node type, or statement word (c4 person, tree dir). at most 2000 characters. |
| `operations[].options` | `object` | no |  |
| `operations[].statement` | `string` | no | add_node: the whole line, for a kind with no plain node statement. at most 2000 characters. |
| `operations[].into` | `string \| null` | no | A block; null is the top level. |
| `operations[].after` | `string` | no | at most 2000 characters. |
| `operations[].arrow` | `"<-->" \| "-->" \| "<->" \| "..>" \| "->" \| "--"` | no |  |
| `operations[].find` | `string` | no | at most 2000 characters. |
| `operations[].replace` | `string` | no | at most 2000 characters. |
| `operations[].all` | `boolean` | no |  |
| `svg` | `"auto" \| "always" \| "never"` | no | never (the default) draws nothing; auto or always draws like draw_diagram. default "never". |
| `themes` | `"light" \| "dark" \| "both"` | no | light, dark, or both (the default): the light picture and the dark one a dark page needs. default "both". |
| `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 |
|---|---|---|---|
| `source` | `string` | yes | The edited source. Lines no operation touched are byte for byte as they were, comments included. |
| `changed` | `boolean` | yes |  |
| `results` | `object[]` | yes | One entry for each operation, in order. |
| `results[].op` | `"rename" \| "set" \| "add_node" \| "remove" \| "add_edge" \| "remove_edge" \| "move" \| "replace_text"` | yes |  |
| `results[].applied` | `boolean` | yes |  |
| `results[].lines` | `integer[]` | yes | Lines of the new source this operation wrote, or the lines it removed from. |
| `results[].message` | `string` | yes |  |
| `results[].hint` | `string \| null` | yes |  |
| `valid` | `boolean` | yes |  |
| `kind` | `string \| null` | yes |  |
| `errors` | `Diagnostic[]` | yes |  |
| `errors[].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. |
| `errors[].severity` | `"error" \| "warning"` | yes | Errors stop rendering; warnings never do. |
| `errors[].message` | `string` | yes | What is wrong, in one sentence. |
| `errors[].line` | `integer` | yes | 1-based line in the submitted source. minimum 1. |
| `errors[].column` | `integer` | yes | 1-based column in that line. minimum 1. |
| `errors[].length` | `integer` | yes | Number of characters the problem covers. minimum 1. |
| `errors[].hint` | `string \| null` | yes | A concrete suggestion for fixing it, or null. |
| `warnings` | `Diagnostic[]` | yes | Quality warnings; only when the result is drawn. |
| `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. |
| `summary` | `string \| null` | yes |  |
| `outline` | `string[]` | yes |  |
| `outlineTruncated` | `boolean` | yes |  |
| `size` | `Size \| null` | yes |  |
| `renders` | `object[]` | yes |  |
| `renders[].theme` | `"light" \| "dark"` | yes |  |
| `renders[].svg` | `string` | yes |  |
| `renders[].size` | `Size` | yes | Natural size of a rendered diagram in px. |
| `renders[].size.width` | `integer` | yes | Width in px. minimum 1. |
| `renders[].size.height` | `integer` | yes | Height in px. minimum 1. |
| `picturesOmitted` | `object` | no | Present only when pictures were left out because the answer would have been too big for an AI client to read in one piece. |
| `picturesOmitted.themes` | `("light" \| "dark")[]` | yes | The color schemes whose pictures were left out. |
| `picturesOmitted.characters` | `integer` | yes | How many characters the pictures left out came to. |
| `picturesOmitted.limit` | `integer` | yes | The most characters one answer may hold before the pictures are left out. |
| `picturesOmitted.why` | `string` | yes | Why they were left out, and what to do. |
| `viewUrl` | `string` | no | A link that shows a valid diagram in a browser; give it to the person who wants to look. The source is in the part after #, never sent to a server, but anyone with the link can read it. Absent when too long; next says so. |
| `svgUrl` | `string` | no | The viewUrl with &download=svg: a person opens it to download the SVG. Not a file address for curl; use saveCommand. Absent when too long. |
| `saveCommand` | `string` | no | Run in a shell to save the SVG into the repository: the CLI decodes the link locally, fetches nothing, and embeds the source. Set --out to the path; add --theme dark for dark. Absent when too long. |
| `next` | `string` | yes |  |

## Behavior hints

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

## Bounds

A bound that is reached is reported in the result; nothing is cut silently.

| Bound | Value | What it limits |
|---|---|---|
| `maxEditOperations` | 50 | Operations in one call. |
| `maxEditTextLength` | 2000 | Characters in one field of an operation, such as a statement, a find, or a replacement. |

## See also

| Doc | Why |
|---|---|
| [Tool reference](https://docs.plotwork.dev/mcp/tools.md) | Every tool, with the workflows first |
| [`POST /v1/diagrams/edit`](https://docs.plotwork.dev/api/post-v1-diagrams-edit.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 |