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ChartAnt

by net.chartant
OverviewDiscussionsAdmin

Heatmap

generate_heatmap_chart
Read-onlyIdempotent

Draw a heatmap: a grid of cells coloured by value, with x and y categories (e.g. weekday × hour, product × region). For one cell per calendar day use generate_calendar_heatmap. Returns a hosted PNG link, a share page, alt text and editable PowerPoint/Excel links.

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": {
      "data": "<data>"
    },
    "name": "generate_heatmap_chart"
  }
}

Input Schema

NameRequiredDescriptionDefault
dataYesOne row per cell: {x, y, value}; x and y are category names or numbers.
themeNodefault (light) or dark background.
titleNoTitle shown above the chart.
widthNoImage width in pixels (default 720).
heightNoImage height in pixels (default 480).
brandThemeNoName of a brand theme saved on the user's account (their colours and footer), only when the user asks for their theme. Or "colorblind" for colours that people with colour-vision deficiency can tell apart (anyone can use it).

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observed

TDQS

A4.3/5.0
Behavior4/5

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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description earns credit for disclosing the return artifacts (hosted PNG link, share page, alt text, editable PowerPoint/Excel links) despite no output schema existing. It omits any mention of the 5000-cell cap or generation cost, which are the remaining behavioral gaps.

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?

Three tightly packed sentences with no filler: what it draws, the alternative for a different case, and what comes back. Purpose and the useful category examples are front-loaded before the sibling reference.

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?

For a chart-generation tool with full schema coverage and no output schema, the description covers the missing pieces: the visual semantics, the sibling routing, and the return payload. Nothing an agent needs to choose and call this tool correctly is absent.

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 description coverage is 100%, so every parameter including theme, brandTheme, width and height is already documented in the schema, establishing the baseline of 3. The description's only added meaning is illustrative examples of x/y category pairs (weekday × hour, product × region), which clarify data intent but add no parameter syntax or format detail beyond the schema.

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?

"Draw a heatmap" gives a specific verb and resource, and the description immediately defines the visual model ("a grid of cells coloured by value, with x and y categories") so an agent knows exactly what output shape to expect. It also names the confusable sibling, generate_calendar_heatmap, making the boundary between the two unambiguous.

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?

It gives an explicit routing rule: for one cell per calendar day use generate_calendar_heatmap instead, which resolves the only genuinely ambiguous sibling choice. It does not address when a heatmap is preferable to other chart families (scatter, treemap, bar), but that distinction follows from the stated x/y-category structure.

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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