dgmo-mcp
OfficialTurn conversations into diagrams by rendering, validating, and sharing DGMO markup, with tools for AI-assisted generation and handoff to editors.
Render DGMO markup to SVG or PNG locally (
render_diagram).Validate DGMO syntax quickly without rendering (
validate_diagram).Suggest suitable chart types from plain-English prompts (
suggest_chart_type).List all supported chart types, including beta (
list_chart_types).Fetch DGMO language reference for accurate syntax (
get_language_reference).Get worked examples per chart type as few-shot references (
get_examples).Create shareable diagrammo.app URLs without uploading (
share_diagram).Open diagrams directly in the Diagrammo desktop app for live editing (
open_in_app).Check if the desktop app is installed (
check_app_installed).Preview one or more diagrams in an HTML browser view (
preview_diagram).Generate polished multi-section HTML reports with diagrams (
generate_report).
@diagrammo/dgmo-mcp
Turn a conversation into a real diagram — without leaving your AI tool.
This MCP server gives Claude (and any MCP-compatible AI tool) the ability to render sequence diagrams, flowcharts, ER diagrams, C4 architecture, gantt charts, and 40+ other chart types from concise text markup — then hand the result off to a full editor for refinement. Ask for a diagram in chat; get a real one back.
What you can do
Ask in plain language — "diagram the auth flow as a sequence", "chart the Q3 plan as a gantt", "draw our services as a C4 diagram" — and Claude writes the markup and renders it. The markup stays readable and diffable:
flowchart Mutiny Resolution
direction-tb
[Sail] Set sail under the captain
{Trouble?} Discontent in the crew?
{Vote} Crew vote called
[Mutiny] Seize the ship
(Sail) -> (Trouble?)
(Trouble?) -Yes-> (Vote)
(Vote) -Mutiny-> (Mutiny)→ renders to the flowchart above. All rendering happens locally — no diagram data leaves your machine.
Related MCP server: drawio
Tools
Tool | What it does | Over HTTP |
| Render DGMO markup to SVG or PNG | yes |
| Check markup and report parse errors, without rendering | yes |
| Suggest the chart types that fit a description | yes |
| List all supported chart types, marking the beta ones | yes |
| Get DGMO syntax documentation for accurate generation | yes |
| Fetch worked examples for a chart type | yes |
| Get a shareable diagrammo.app URL — hand your diagram to the web editor | yes |
| Open the diagram straight into the Diagrammo desktop app for editing | no |
| Report whether the desktop app is installed | no |
| Render one or more diagrams and open an HTML preview in the browser | no |
| Build a polished multi-section HTML report with ToC and optional source | no |
share_diagram and open_in_app are the bridge out of chat: a diagram Claude generates
becomes something you can refine, restyle, and embed — see below.
The four marked no open a browser or launch the desktop app. Over HTTP that would happen on the machine running the server rather than on yours, so they are not offered there — see Serving over HTTP.
Beyond the MCP server
The MCP server is one entry point into Diagrammo — a whole ecosystem built on the same DGMO markup. Generate in chat, refine in a real editor, embed anywhere:
diagrammo.app — the desktop app.
open_in_appdrops an AI-generated diagram straight into it, with live preview, palettes, and export.online.diagrammo.app — a full editor in the browser, zero install.
share_diagramURLs open right here.Docs integrations — drop DGMO fenced code blocks into your docs site: remark-dgmo, astro-dgmo, docusaurus-plugin-dgmo, fumadocs-dgmo.
Obsidian — the Diagrammo Diagrams community plugin renders DGMO in your vault.
CLI —
npx @diagrammo/dgmo-cli file.dgmo -o out.png, or install it withnpm install -g @diagrammo/dgmo-cli(macOS and Linux).
One markup, everywhere. A diagram you generate here renders identically in the app, in your docs, and in Obsidian — because they all speak DGMO.
→ Try it free at diagrammo.app
Setup
Easiest — one command
Install the dgmo CLI and let it wire everything up:
npm install -g @diagrammo/dgmo-cli # macOS and Linux
dgmo install # auto-detects Claude Code, Codex, Claude Desktop, Cursor, …Prefer Homebrew or pacman? See diagrammo.app/dev.
dgmo install configures each detected assistant non-interactively and points it at dgmo mcp, so there's no separate package to install or prompts to answer. Target one surface with dgmo install claude-code (or codex, claude-desktop, …).
Manual configuration
Prefer to edit configs yourself? Point any MCP client at the server via npx (no global install needed):
Claude Code — .claude/settings.local.json; Claude Desktop — ~/Library/Application Support/Claude/claude_desktop_config.json:
{
"mcpServers": {
"dgmo": {
"command": "npx",
"args": ["-y", "@diagrammo/dgmo-mcp"]
}
}
}If you have the dgmo CLI installed, { "command": "dgmo", "args": ["mcp"] } works too. Restart the client after saving — the tools appear automatically.
Serving over HTTP
The setups above launch the server as a child process and talk to it over its standard input and output. That needs the server and the client on the same machine. Where they are not — a hosted agent platform, a container, one server shared by several people — start it as an HTTP endpoint instead:
npx -y @diagrammo/dgmo-mcp --http # http://127.0.0.1:3333/mcp
MCP_TRANSPORT=http MCP_PORT=8080 npx -y @diagrammo/dgmo-mcpEvery option takes a flag or an environment variable, whichever your setup can express:
Flag | Variable | Default | What |
|
| off | Serve streamable HTTP instead of stdio |
|
|
| Port to listen on |
|
|
| Interface to bind |
|
|
| Path the endpoint answers on |
|
| loopback | Extra |
|
| unset |
|
Each request is served independently — no sessions, nothing kept between calls — so one endpoint can serve several clients at once.
The server has no authentication of its own. It binds loopback by default and rejects requests carrying a
Hostheader it was not told to expect, which is enough for a client on the same machine or inside the same container. Anything reachable from a wider network needs your own authentication in front of it, and--allow-hostfor the hostname it will be reached by. Binding a non-loopback interface without naming a host prints a warning saying so.
--help prints all of this from the installed version.
Privacy
All rendering is local. Your diagram markup and the images it produces never leave
your machine, except when you explicitly call share_diagram (which encodes the diagram
into a diagrammo.app URL). See the privacy terms.
Dev hub (AI-tuning tools)
pnpm hubOne command, one server, one browser tab. The hub opens a tabbed shell over the three AI-tuning dev tools — switch between them with the top tabs, no separate ports or commands to remember:
Trigger tuning — edit the phrase/concept vocabulary that drives
suggest_chart_type, score prompts live, save back totriggers.json.LLM judge — judge chart-type descriptions against prompts with
claude -p.Guidance studio — author the per-type styling guidance the server delivers (the
<!-- TIPS -->blocks in dgmo'slanguage-reference.md, sliced intoget_language_reference): pick a type, edit how the AI is told to style it, run a prompt against a committed dataset fixture (so inputs never move between runs), and see the generated DGMO + rendered image side by side. The picker doubles as a coverage bar; "Compare 3×" renders no-guidance vs your tips for a by-eye check; Save validates and writes back tolanguage-reference.md.
These tools are dev-only and never bundled into the published server. (The
standalone pnpm harness and pnpm studio scripts still run a single tool each
if you ever want one in isolation.)
Contributing & releases
Development setup and the release workflow live in CONTRIBUTING.md.
License
MIT
Available Tools
11 toolscheck_app_installedARead-only
Check whether the Diagrammo desktop app is installed. Returns a sentence naming the output route the product prefers, plus JSON { installed, paths, platform }. Detection is macOS-only; other platforms always report not installed. The answer does not change within a session, so one call is enough before deciding how to show a diagram: when installed, the preferred route is open_in_app with filePath; otherwise share_diagram.
| Name | Required | Description | Default |
|---|---|---|---|
No parameters | |||
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Beyond the readOnly/non-destructive annotations, it discloses three non-obvious traits: detection is macOS-only with other platforms always reporting not installed, the result is stable within a session so caching is safe, and the return is a prose sentence plus a JSON object with named keys.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Three sentences, front-loaded with the core purpose, then output shape, then the platform caveat and decision rule. No filler and every clause carries actionable information.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
With no output schema, the description compensates by naming the return shape (sentence plus { installed, paths, platform }), and it supplies the decision context the agent needs. Nothing required to call it correctly is missing.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
This tool takes zero parameters, so there is nothing to document and the baseline is 4. The mention of `filePath` refers to open_in_app's parameter, not this tool's, so it neither helps nor hurts.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description states a specific verb and resource ('Check whether the Diagrammo desktop app is installed') and immediately distinguishes itself from sibling tools like open_in_app and share_diagram by naming them as the consumers of its result.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
It gives explicit when-to-use guidance ('one call is enough before deciding how to show a diagram') and a complete decision rule: installed → open_in_app with `filePath`, otherwise → share_diagram. When-not-to-use is implied by the session-stable note, which tells the agent not to call repeatedly.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
generate_reportA
Generate a polished HTML report with multiple DGMO diagrams, table of contents, and optional source blocks. Opens in browser by default. For DGMO syntax call get_language_reference.
| Name | Required | Description | Default |
|---|---|---|---|
| open | No | Open the report in the browser | |
| theme | No | Color theme | light |
| title | Yes | Report title | |
| palette | No | Color palette | slate |
| sections | Yes | Report sections, each with a diagram | |
| subtitle | No | Optional subtitle | |
| include_source | No | Show DGMO source in collapsible blocks |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover safety (readOnlyHint=false, destructiveHint=false) and open-world behavior, but the description adds specific context: the tool opens the report in a browser by default and produces an HTML report with optional source blocks. This goes beyond the generic openWorldHint, though it doesn't detail file persistence or permissions.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Three sentences, front-loaded with the core action, followed by a key behavioral note and a helpful cross-reference. Every sentence earns its place with no redundancy.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a report-generation tool with no output schema, the description covers the output format (HTML report with TOC and diagrams), key behavior (opens in browser), and points to syntax reference. It lacks details on return value (e.g., file path) or file saving location, but the rich schema compensates sufficiently.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, so the schema fully documents all parameters. The description mentions multiple diagrams, table of contents, and optional source blocks, which loosely map to sections and include_source, but adds no syntax or format details beyond what the schema already provides.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description states a specific verb (Generate) and resource (HTML report) with key features (multiple DGMO diagrams, table of contents, optional source blocks). It clearly distinguishes this tool from sibling diagram tools like render_diagram or preview_diagram by focusing on multi-section report generation.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description only points to get_language_reference for DGMO syntax, which is a sub-task aid rather than guidance on when to use this tool versus alternatives. Usage is implied (for creating reports) but no explicit when/when-not or alternative selection criteria are provided.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
get_examplesA
Get example DGMO diagrams for a chart type. Returns real-world examples from the gallery that demonstrate syntax patterns. Use these as few-shot references when generating new diagrams.
| Name | Required | Description | Default |
|---|---|---|---|
| chart_type | No | Chart type to get examples for (e.g. "sequence", "infra", "bar"). Omit to list all available example names. |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It states it returns real-world examples, but does not mention behavior when the parameter is omitted (lists all names) or any read-only implications. Adequate but not fully transparent.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two short, front-loaded sentences with no redundancy. Every phrase earns its place.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a tool with one optional parameter and no output schema, the description fully explains purpose, return content, and usage context. Complete for its complexity.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema coverage is 100%, so the description does not need to add much. It provides example values and tells to omit for listing names, which adds slight value beyond the schema. Baseline 3 is appropriate.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the action ('get'), the resource ('example DGMO diagrams for a chart type'), and the purpose ('few-shot references'). It is specific and distinguishes from siblings like generate_report or validate_diagram.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description explicitly says 'Use these as few-shot references when generating new diagrams,' indicating when to use. It does not explicitly state when not to use or mention alternatives, but the context makes it clear.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
get_language_referenceARead-onlyIdempotent
Get the DGMO language reference. With chart_type, returns that type's section plus the universal rules every diagram follows (the closed color set, titles, categorize-and-color). Without it, returns the entire reference for all chart types, which is very large (hundreds of KB); pass chart_type whenever the type is known. Errors when the type has no documented section — call list_chart_types for the valid ids. suggest_chart_type already appends the chosen type's section, so a call here is only needed after the user picks a type or when switching types.
| Name | Required | Description | Default |
|---|---|---|---|
| chart_type | No | Optional chart type to get reference for (e.g. "sequence", "flowchart", "bar") |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly/idempotent/non-destructive, but the description adds genuinely new behavioral context: the no-argument call returns a very large payload (hundreds of KB), an error occurs for undocumented types, and the returned content includes universal rules (color set, titles, categorize-and-color). This is exactly the kind of cost/error/redundancy disclosure annotations cannot carry.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Three dense sentences, front-loaded with the core action before the conditional behavior and the sibling-avoidance note. Every clause carries information; it is slightly long but no sentence is filler.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
No output schema exists, so the description must describe return values, and it does: the type section plus universal rules, or the full reference. Error behavior, alternatives, and payload-size trade-offs are all covered, leaving nothing an agent needs to call it correctly.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema coverage is 100%, so the baseline is 3; the description goes beyond it by explaining the effect of the parameter (returns that type's section plus universal rules), the consequence of omitting it (entire reference, very large), and the failure mode (errors for undocumented types, ids via list_chart_types). Only the absence of example id syntax keeps it from a 5.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
States a specific verb and resource ('Get the DGMO language reference') and precisely scopes the two modes of operation (with vs. without chart_type). It explicitly distinguishes itself from siblings suggest_chart_type and list_chart_types, so an agent can route correctly without opening any schema.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
Gives explicit when-to-use guidance ('pass chart_type whenever the type is known'), a when-not ('suggest_chart_type already appends the chosen type's section, so a call here is only needed after the user picks a type or when switching types'), and names the fallback tool for error recovery (list_chart_types for valid ids).
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
list_chart_typesARead-onlyIdempotent
List all supported DGMO chart types with descriptions.
| Name | Required | Description | Default |
|---|---|---|---|
No parameters | |||
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds minimal behavioral context beyond stating the content (chart types with descriptions). It does not contradict annotations, but it also does not elaborate on traits like return format or error states.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single sentence of 6 words, conveying the essential purpose without any extraneous information. It is front-loaded and efficient.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the simplicity of the tool (no parameters, annotations present, no output schema), the description is largely complete. It informs the agent what the tool does and what content to expect. However, it could hint at the output structure (e.g., 'returns an array of chart type objects with name and description'). Still, it is sufficient for an agent to understand the tool's purpose.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
No parameters exist, so schema coverage is 100%. The description adds context by specifying that the list includes descriptions, which adds meaning beyond the empty schema. Baseline for 0 params is 4.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description 'List all supported DGMO chart types with descriptions' clearly states the verb (list), the resource (chart types), and the scope (all supported, with descriptions). It distinguishes from sibling tools like 'suggest_chart_type' which is for recommendations, not listing.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
Usage is implied: use to get a list of chart types. However, there is no explicit guidance on when to use versus alternatives such as 'suggest_chart_type', nor any exclusions or prerequisites, so the description lacks clear context for selection.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
open_in_appA
Open a DGMO diagram in the Diagrammo desktop app (macOS only). Falls back to browser preview if the app is not installed. Pass filePath to open a saved .dgmo file directly — the app opens THAT file, so in-app edits autosave back to it (one editable source of truth, live re-render). This is the preferred path when the app is installed: write the .dgmo source first, then open it here. Omit filePath for an ephemeral diagram (sends a deep link; the app creates its own copy).
| Name | Required | Description | Default |
|---|---|---|---|
| dgmo | Yes | DGMO diagram markup | |
| filePath | No | Absolute path to an already-saved .dgmo file. When set, the app opens this exact file for live editing instead of receiving a deep-linked copy. |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations are minimal (readOnlyHint, destructiveHint, openWorldHint). The description adds critical behavior: macOS only, fallback to browser preview, filePath autosaving and live re-render, and the distinction between ephemeral and persistent modes.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Five sentences, front-loaded with the main action and platform. Every sentence adds essential information without redundancy or filler.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
No output schema, but the description explains the two modes and fallback. It covers platform restriction and file persistence. Could mention installation requirement more explicitly, but 'preferred path when app is installed' implies it.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema coverage is 100% with descriptions. The description adds value by explaining that filePath opens the exact file for live editing (source of truth) and that dgmo is the markup. This enriches the basic schema definitions.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description specifies the verb 'open', the resource 'DGMO diagram', and the platform 'macOS only'. It distinguishes from sibling tools like 'preview_diagram' by noting fallback behavior and file handling.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides clear guidance on when to use filePath (for saved files with live editing) vs omit (ephemeral diagram). It implicitly contrasts with preview_diagram as fallback, but does not explicitly list when not to use.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
preview_diagramA
Render one or more DGMO diagrams and open an HTML preview in the browser. Supports theme toggle and optional source display. For DGMO syntax call get_language_reference.
| Name | Required | Description | Default |
|---|---|---|---|
| theme | No | Color theme | light |
| palette | No | Color palette | slate |
| diagrams | Yes | One or more diagrams to preview | |
| include_source | No | Show DGMO source in collapsible blocks |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint false and openWorldHint true, signaling a non-read-only, external-interacting operation. The description adds that it opens an HTML preview in the browser, which aligns with openWorldHint, but does not clarify permissions, temporary file side effects, or rate limits. It offers modest context beyond the annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two sentences plus a routing pointer, front-loaded with the primary action and output medium. Every sentence earns its place; the syntax pointer prevents misuse and is not redundant.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a simple preview tool with full schema coverage and no output schema, the description covers the essential behavior and optional features. It omits usage comparisons, but overall it is complete enough for correct invocation.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, so all four parameters are fully documented in the schema. The description mentions theme toggle and optional source display, mapping to theme and include_source, but adds no format or syntax detail beyond what the schema provides. Baseline 3 is appropriate.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
States a specific verb ('Render') and resource ('DGMO diagrams'), and names the output medium ('open an HTML preview in the browser'). It does not explicitly distinguish from siblings like render_diagram or open_in_app, but the scope is clear enough for selection.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
Provides a pointer for syntax ('call get_language_reference'), which is a prerequisite note rather than when-to-use guidance for this tool. There is no explicit comparison to alternatives like render_diagram, share_diagram, or open_in_app; usage is only implied by the tool name and purpose.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
render_diagramARead-onlyIdempotent
Render DGMO markup to SVG or PNG. Returns SVG text or base64 PNG image. When format is "png", also saves the image to a temp file and returns the path. For DGMO syntax call get_language_reference.
| Name | Required | Description | Default |
|---|---|---|---|
| dgmo | Yes | DGMO diagram markup. For syntax call get_language_reference. | |
| theme | No | Color theme | light |
| width | No | Canvas width in px. Omit to let the diagram size itself from its content. Honoured exactly by the chart types that lay their content out into the canvas (bar, line, pie and the other data charts). A chart that sizes itself from its own nodes — org, sitemap, class, er, infra and the rest of the structured family — cannot go below its content and will return a wider canvas than asked for. | |
| format | No | Output format | svg |
| height | No | Canvas height in px. Most chart types derive height from their content and ignore this; the data charts honour it. | |
| palette | No | Color palette (slate, atlas, blueprint, tidewater, nord, catppuccin, tokyo-night) | slate |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered. The description adds genuinely useful behavior beyond that: the return shape (SVG text vs base64 PNG) and the side effect that PNG format writes a temp file and returns its path. It still doesn't mention failure behavior for invalid markup.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Three short sentences, front-loaded with the primary action and output formats, with no filler. The final syntax-pointer sentence is somewhat redundant with the schema's own note but still earns its place as a routing hint.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
With no output schema, the description correctly shoulders the return-value burden (SVG text or base64 PNG, plus temp file path). Given six parameters and a rendering operation, the main remaining gap is error/validation behavior, which is minor for a read-only render tool.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, including detailed notes on width/height sizing and palette options, so the schema carries the parameter burden. The description only marginally extends this by tying the 'png' format value to the temp-file side effect. Baseline 3 is appropriate.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
States a specific verb (Render) and resource (DGMO markup) plus the output formats (SVG or PNG), so an agent knows exactly what the tool produces. It does not, however, differentiate itself from close siblings like preview_diagram or validate_diagram, which an agent might reasonably confuse it with.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The only routing guidance is 'For DGMO syntax call get_language_reference', which points to a dependency rather than explaining when to pick this tool over preview_diagram or validate_diagram. Usage context is implied by the name but never stated.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
suggest_chart_typeA
Suggest the best DGMO chart type for a user's plain-English diagram request.
Call this first when creating a new diagram: it ranks the chart types against the request and, on a confident pick, appends that type's language-reference section, so no separate get_language_reference call is needed. It is not needed when editing an existing diagram, whose first line already declares its type.
Returns one of two shapes: (1) a confident pick (high/medium) with the top match's syntax, or (2) an '⚠️ ASK THE USER' result when the choice is ambiguous or nothing matched. On an ASK-THE-USER result, present the listed candidates to the user and wait for their choice before generating, because the request alone does not settle which type they want.
| Name | Required | Description | Default |
|---|---|---|---|
| prompt | Yes | User's plain-English diagram request |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations present, the description carries the full behavioral burden and does so well: it discloses the hidden side effect of appending the language-reference section, defines both possible return shapes including the '⚠️ ASK THE USER' outcome, and prescribes agent behavior on that outcome. This is well beyond what structured fields provide.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Content is front-loaded with the core purpose and the when-to-call rule, and the result-shape and ASK-THE-USER guidance are placed last where they belong. Slightly dense, but essentially every sentence carries decision-relevant information.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
There is no output schema, and the description compensates by spelling out the two return shapes and the required agent action for each. Combined with the explicit when/when-not guidance, an agent has everything needed to call and act on this tool correctly.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100% for the single 'prompt' parameter, so the schema already documents it as the user's plain-English diagram request. The description adds no syntax, format, or length guidance beyond that, so baseline 3 applies.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description states a specific verb and resource (suggest the best DGMO chart type) and scopes it to a plain-English diagram request. It clearly distinguishes itself from siblings like get_language_reference and list_chart_types by describing what it returns and why a separate reference call is unnecessary.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
It gives an explicit call-first rule for new diagrams, states the negative case (not needed when editing an existing diagram, whose first line declares its type), and names the alternative it subsumes (get_language_reference). It also tells the agent what to do on an ambiguous result: present candidates and wait for the user.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
validate_diagramA
Validate DGMO markup without rendering. Returns structured parse errors and warnings. Much faster than render_diagram — use this to check syntax before rendering.
| Name | Required | Description | Default |
|---|---|---|---|
| dgmo | Yes | DGMO diagram markup to validate |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations exist, so the description bears full responsibility. It discloses that the tool does not render and returns structured errors/warnings, and that it is faster. While it doesn't discuss auth or rate limits, these are less critical for a validation tool. A minor omission: it could explicitly state that it does not modify data, but 'without rendering' implies no side effects.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is two concise sentences, front-loads the purpose, and contains no extraneous information. Every sentence adds value.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's simplicity (one required parameter, no output schema), the description fully covers what the tool does, when to use it, and what it returns. No gaps remain.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%: the parameter 'dgmo' is described as 'DGMO diagram markup to validate'. The description adds no additional parameter-level detail beyond the schema. Per guidelines, baseline is 3 when schema coverage is high.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the verb 'validate' and the resource 'DGMO markup', and specifies it returns structured parse errors and warnings. It effectively distinguishes from sibling tools like render_diagram by noting it does not render.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description explicitly says to use this tool to check syntax before rendering and mentions it's much faster than render_diagram. This provides clear when-to-use guidance and contrasts with an alternative.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Tool Schema Changelog
Recent tool additions, removals, and schema changes observed during successful MCP inspections.
3 tool updates
v0.29.5- Changed
generate_report1 field changed- changed
Input schema / properties / sections / items / properties / dgmo / descriptionPrevious value: -"DGMO diagram markup. Color a label by appending a lowercase color name as the trailing token (e.g. \"Sales red\"); capitalize (\"Red\") to use a color word as literal text."New value: +"DGMO diagram markup. For syntax call get_language_reference."
- Changed
preview_diagram1 field changed- changed
Input schema / properties / diagrams / items / properties / dgmo / descriptionPrevious value: -"DGMO diagram markup. Color a label by appending a lowercase color name as the trailing token (e.g. \"Sales red\"); capitalize (\"Red\") to use a color word as literal text."New value: +"DGMO diagram markup. For syntax call get_language_reference."
- Changed
render_diagram1 field changed- changed
Input schema / properties / dgmo / descriptionPrevious value: -"DGMO diagram markup. Color a label by appending a lowercase color name as the trailing token (e.g. \"Sales red\"); capitalize (\"Red\") to use a color word as literal text."New value: +"DGMO diagram markup. For syntax call get_language_reference."
1 tool update
v0.29.1- Changed
render_diagram2 fields changed- added
Input schema / properties / heightAdded value: +{ + "description": "Canvas height in px. Most chart types derive height from their content and ignore this; the data charts honour it.", + "exclusiveMinimum": 0, + "type": "integer" +} - added
Input schema / properties / widthAdded value: +{ + "description": "Canvas width in px. Omit to let the diagram size itself from its content. Honoured exactly by the chart types that lay their content out into the canvas (bar, line, pie and the other data charts). A chart that sizes itself from its own nodes — org, sitemap, class, er, infra and the rest of the structured family — cannot go below its content and will return a wider canvas than asked for.", + "exclusiveMinimum": 0, + "type": "integer" +}
1 tool update
v0.17.0- Added
render_diagram
1 tool update
v0.12.0- Removed
render_diagram
2 tool updates
v0.9.1- Changed
generate_report1 field changed- changed
Input schema / properties / theme / defaultPrevious value: -"dark"New value: +"light"
- Changed
preview_diagram1 field changed- changed
Input schema / properties / theme / defaultPrevious value: -"dark"New value: +"light"
TDQS
Scored across 11 tools
Most tools have distinct purposes, but preview_diagram and generate_report both render multiple diagrams and open a browser, creating potential overlap. render_diagram, open_in_app, and share_diagram are clearly differentiated by output medium and use case. The reference/information tools (get_language_reference, list_chart_types, get_examples, suggest_chart_type) are distinct enough in their guidance.
All tool names follow a consistent snake_case verb_noun pattern: check_app_installed, get_language_reference, preview_diagram, share_diagram, list_chart_types, open_in_app, render_diagram, get_examples, validate_diagram, generate_report, suggest_chart_type. The minor variation in open_in_app (verb_preposition_noun) does not break predictability.
With 11 tools, the set is well-scoped for a diagramming server. Each tool serves a clear role: discovery, validation, rendering, previewing, sharing, app integration, and reporting. No extraneous or missing tools inflate or thin the surface.
The tool surface covers the core diagram lifecycle: type suggestion, reference/examples, validation, rendering, previewing, sharing, and in-app editing. A minor gap is the absence of an explicit file-writing or save-diagram tool, though open_in_app and render_diagram partially address this. Overall, the coverage is strong for the stated domain.
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