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ChartAnt

by net.chartant
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Small multiples

generate_small_multiples
Read-onlyIdempotent

Draw the same small chart once per group (country, product, team) in a grid, all on one shared scale, so the groups can be compared at a glance. Rows are {group, x, value}, e.g. {group:'France', x:'Jan', value:120}. Up to 24 groups. For a few groups on one chart use generate_line_chart with group. 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_small_multiples"
  }
}

Input Schema

NameRequiredDescriptionDefault
dataYesOne row per group and x value; each group gets its own small chart.
unitNoUnit for the legend, e.g. 'EUR', 'users', '%'.
chartNoDefault line.
titleNoTitle shown above the map.
columnsNoCharts per row in the grid (chosen automatically when left out).
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

A4.5/5.0
Behavior4/5

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

Annotations already declare readOnlyHint, idempotentHint and non-destructive behavior, so the safety profile is covered. The description goes beyond them by disclosing the output artifacts ('hosted PNG link, a share page, alt text and editable PowerPoint/Excel links') and the shared-scale constraint that shapes the render. It stops short of stating failure modes or what happens when group count is exceeded, which keeps it off a 5.

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?

Four short sentences, front-loaded with the core behavior and scale semantics before the example, the limit, the alternative and the outputs. No sentence is filler; each adds either a constraint, a routing rule, or a return-value fact.

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 six-parameter chart generator with no output schema, the description covers the concept, the data shape, the group ceiling, the sibling alternative, and the full return set. Nothing an agent needs to select or invoke it correctly is missing.

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 (data, unit, chart, title, columns, brandTheme) is already documented in the schema, setting the baseline at 3. The description reinforces the row shape with a concrete literal, {group:'France', x:'Jan', value:120}, which is a mild aid for payload construction but largely restates the item schema rather than adding new semantics.

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 ('draw the same small chart once per group in a grid, all on one shared scale') plus the comparison intent, and immediately distinguishes itself from the sibling that handles grouped single charts. An agent can tell exactly what this produces without opening the schema.

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

Usage Guidelines5/5

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

Gives an explicit routing rule: 'For a few groups on one chart use generate_line_chart with group,' which names the alternative and the condition selecting it. It also states a hard applicability bound ('Up to 24 groups') and typical group dimensions (country, product, team), so the agent knows when this tool is appropriate and when it is not.

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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