Line9

Render diagram

render_diagram

Read-onlyIdempotent

Render Mermaid source with Line9's layout engine. Call this whenever you write or change Mermaid and the user should see the result. Flowcharts and sequence diagrams get Line9's layout; other Mermaid kinds are rendered with Mermaid's own layout and flagged as such. Returns a short verdict — kind, size, warnings, or a parse error with its line and column — plus an "Open in Line9" link. On a parse error, fix the named line and call again. Assistants that support MCP Apps show the diagram in a panel; there, do not paste the SVG or repeat the source in your reply. In an assistant with no panel (a terminal or editor), reply with the verdict line and the open_url link — that link is the only way the user sees the diagram. Write flowcharts as flowchart LR unless the user asks for top-to-bottom; chat panels are wide and short. No sign-in needed; renders carry a small Line9 mark unless the user is signed in to Line9 Pro. Set theme, orientation, spacing and legend in the source itself (line9: frontmatter; flowchart LR), never as arguments. This connector cannot publish or save. To publish, the user opens the diagram in Line9 (the open_url link) and publishes there — not with the Line9 CLI.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`plan`	No	Opaque plan from a previous result (widget use). A hint only: skips the solve when it still fits the source.
`source`	Yes	Mermaid source. Optional YAML frontmatter is honoured — set it in the source, never as arguments: `title`, and a nested `line9:` block with `theme` (one of `boardroom`, `linen`, `blueprint`), `scale: { node, spacing }` and `flowchart: { legend: on \| off }`. The flowchart direction directive is also honoured. Maximum 100000 characters.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`svg`	No
`path`	No
`plan`	No
`error`	No
`width`	No
`config`	No
`height`	No
`source`	No
`status`	Yes
`diagram`	No
`controls`	No
`diagrams`	No
`open_url`	No
`warnings`	No
`signed_in`	No
`truncated`	No
`watermark`	No
`edge_count`	No
`node_count`	No
`orientation`	No
`render_mode`	No
`stop_reason`	No
`diagram_type`	No
`engine_version`	No
`schema_version`	Yes
`fallback_reason`	No
`mermaid_version`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 2, 2026

changedOutput schema / properties / fallback_reason / enum

Previous value: -[
-  "unsupported_diagram_kind",
-  "node_cap_exceeded"
-]New value: +[
+  "unsupported_diagram_kind",
+  "node_cap_exceeded",
+  "engine_panic"
+]

First observedSep 17, 2026

TDQS

A4.4/5.0

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), yet the description adds substantial independent context: no sign-in required, a Line9 watermark for non-Pro users, the inability to publish or save, the required source-side configuration, and the panel-vs-terminal reply behavior. This is exactly the value-add a description should provide on top of annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Purpose and the core call trigger are front-loaded, and most sentences carry actionable detail (error re-call loop, panel branching, publish limitation). It is dense and a few clauses could be trimmed, but almost nothing is padding.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Despite an output schema existing, the description wisely explains the verdict shape (kind, size, warnings, parse error with line/column, plus open_url) because agent reply behavior depends on it. Combined with the panel/no-panel branching and publishing constraints, an agent has everything needed to call this correctly and handle the result.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so both parameters are already documented, and the description's 'set it in the source, never as arguments' guidance largely restates the schema's own note on frontmatter. The `plan` parameter — including that it is a hint that may be skipped — is not addressed in the description at all, so baseline 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Render Mermaid source with Line9's layout engine') and immediately scopes the behavior: flowcharts/sequence diagrams get Line9 layout, other kinds fall back to Mermaid's own layout and are flagged. An agent knows exactly what this produces and can distinguish it from the read-only siblings get_diagram/list_diagrams.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicit trigger ('Call this whenever you write or change Mermaid and the user should see the result') plus clear conditional handling: fix the named line on parse error and re-call, and branch replies by whether an MCP Apps panel exists. It does not, however, mention when to prefer the sibling tools get_diagram or list_diagrams, so sibling routing is left to inference.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

All Line9 tools Inspect

Try in Browser

One endpoint for every MCP toolRayrun runs every MCP server behind one URL and holds the credentials. Each call is decided per client, tool, and argument, then recorded.ray.runAd

Glama MCP Gateway

Add one secure layer between your agents and this server.

Resources

Need Help?