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ChartQuery MCP Server

ChartQuery MCP Server

by chartquery
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TypeScript
Hybrid

Chart Render

chart_render
Read-only

Render a saved chart by ID as PNG or SVG, and override datasets, labels, title, width, or height to update the visual without recreating the chart.

Instructions

Chart Render. Render a previously saved chart by ID. Public, no API key required. Supports URL overrides for templates (?data1=, ?labels=, ?title=…).

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "id": "<id>"
    },
    "name": "chart_render"
  }
}

Input Schema

NameRequiredDescriptionDefault
idYesThe chart ID returned in the X-Chart-Render-URL header when saving a chart. Format: cq-xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx.
data1NoOverride first dataset values. Comma-separated numbers. Use data2, data3… for additional datasets.
titleNoOverride the chart title.
widthNoOverride output width in pixels (50–4000).
fieldsNoComma-separated list of fields to keep in the response, with dot notation for nested fields (e.g. name,location.city). Does not change the credit cost.
formatNoOverride output format. Allowed values: png, svg. Default: "png".
heightNoOverride output height in pixels (50–4000).
labelsNoOverride X-axis labels. Comma-separated.

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.0

TDQS

A3.6/5.0
Behavior4/5

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

Annotations already declare readOnlyHint, openWorldHint and non-destructive, so the safety profile is covered. The description adds genuinely new behavioral context: the endpoint is public with no API key required, and query-string overrides are accepted. It stops short of saying what an invalid or expired ID produces.

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?

Three short sentences, front-loaded with the core action, then auth model, then override capability. The opening 'Chart Render.' merely restates the title and is the one line that does not earn its place.

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

Completeness3/5

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

With no output schema, the description carries the burden of explaining what comes back, and it never says whether the result is raw image bytes, a URL, or a rendered artifact — a meaningful gap for a render tool. Annotations and full schema coverage handle most other concerns, so the definition is adequate but not complete.

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 every parameter is already documented with types and constraints such as the 50–4000 pixel bounds and png/svg enum values. The description's mention of ?data1=, ?labels= and ?title= reveals that these parameters double as URL query overrides, a mildly useful framing but not per-parameter meaning beyond the schema.

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

Purpose4/5

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

The description states a specific verb and resource: 'Render a previously saved chart by ID.' The 'previously saved' and 'by ID' qualifiers separate it from chart creation tools like chart_ai or chart, though it never explicitly contrasts with chart_view, which likely also retrieves a saved chart.

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

Usage Guidelines3/5

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

Usage is implied rather than stated: 'previously saved chart' tells the agent a chart must exist first, and the ID requirement narrows it to post-save retrieval. There is no explicit when-to-use versus chart_view or diagram_render, and no statement about what to do if the ID is unknown.

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

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