hex-mcp-server

hex-get-chart-image-from-logic

Retrieve a rendered PNG of a chart cell from a Hex draft session using its cell ID, with optional width and height.

Instructions

Get rendered PNG of a chart cell from the draft session.

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": {
      "cellId": "<cellId>"
    },
    "name": "hex-get-chart-image-from-logic"
  }
}

Input Schema

Name	Required	Description
`width`	No	Image width (100-2000)
`cellId`	Yes
`height`	No	Image height (100-2000)

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.2.0Sep 28, 2026

TDQS

B3.1/5.0

Behavior2/5

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

No annotations are provided, so the description carries the full burden. It usefully discloses the return media type ('PNG'), but says nothing about permissions, whether it triggers/awaits a render, latency, or error behavior when a chart has not been rendered.

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

Conciseness5/5

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

A single sentence with zero wasted words, front-loading the verb and return type. Nothing in it is redundant or padded.

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 annotations and no output schema, the description does cover the essential return type (a PNG image). However, it omits default/expected dimensions, the meaning of cellId, and any linkage to the run-based sibling, leaving invocation details thin for a chart-rendering call.

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

Parameters2/5

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

Schema description coverage is only 67%: width and height are documented with ranges in the schema, but cellId (the sole required parameter) is described nowhere. The description adds no parameter meaning beyond what the schema already supplies and does nothing to compensate for the undocumented cellId.

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?

States a specific verb (get), resource (rendered PNG chart image), and scope (from the draft session). The 'draft session' phrasing implicitly separates it from the sibling hex-get-chart-image-from-run, but it never names that sibling or articulates the distinction outright.

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?

The 'from the draft session' clause implies when this is the right tool versus a run-based variant, but there is no explicit when-to-use/when-not guidance and no named alternative. Usage is inferable rather than stated.

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

Deploy Server