pdfnative-mcp

Add native vector chart

add_chart

Idempotent

Create single-page PDFs with native vector charts: bar, line, area, scatter, pie, donut. Add legends, axes, and data labels in one call.

Instructions

Single-page PDF with a native vector chart (pure path operators, no raster): bar, barH, stackedBar, stackedBarH, line (markers), area, scatter, pie, donut. Multi-series, legends, 'nice' ticks, gridlines, negatives; per-series xValues with xAxis.type 'linear' | 'time' (ISO-8601), secondary right axis (axis2 + yAxis:'right'), axis.scale 'log', dataLabels, labelStride / labelRotation. Pie/donut take exactly one series. Colours are hex ('#3366cc'). Tagged /Figure + /Alt (auto when altText is omitted). Engine cross-field rules surface as CHART_ERROR with the remedy. Inside a longer document use a 'chart' block in generate_basic_pdf. PDF/A (pdfA + embedFonts:true), print, metadata and creationDate as on every document tool.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`axis`	No	Value-axis options (bar/line only).
`pdfA`	No	PDF/A level: pdfa1b (simple text+images), pdfa2b/pdfa2u (richer; 2u = Unicode mapping), pdfa3b (attachments / Factur-X). Pair with embedFonts=true for a valid claim. Exclusive with encryption. See docs/guides/PDFA.md.
`align`	No	Horizontal alignment within the content width. Default 'left'.
`axis2`	No	Secondary RIGHT value axis (drawn only when a series sets yAxis:'right').
`debug`	No	Draw margin / block / cell guide rectangles (unmarked content — not for PDF/UA output). Geometry unchanged. Default false.
`intro`	No	Optional introductory paragraph rendered above the chart. The chart `title` (if any) is also used as the PDF metadata title.
`print`	No	Print production (ISO 32000-1 §14.11): page boxes, `bleed` shorthand (TrimBox = MediaBox inset), crop/registration marks outside the TrimBox, /UserUnit for large formats (PDF 1.7; not under pdfa1b). See docs/guides/PRINT.md.
`title`	No	Chart title rendered above the plot.
`width`	No	Plot width in points (clamped to content width). Default 460.
`xAxis`	No	Horizontal axis. 'category' (default) positions points by index; 'linear' / 'time' position them by series xValues (line/area/scatter only). Time ticks are UTC-deterministic.
`colors`	No	Palette override (per-series for bar/line, per-slice for pie/donut).
`height`	No	Plot-area height in points. Default 240.
`legend`	No	Legend placement. Defaults to 'bottom' for multi-series/pie, else 'none'.
`series`	Yes	Data series. Pie/donut charts use exactly one series (each value becomes a slice).
`strict`	No	Fail with PDF_A_COMPLIANCE_VIOLATION instead of producing a non-conformant PDF/A file (e.g. PDFA_NO_FONT_ENTRIES without embedFonts). Pair with embedFonts=true.
`altText`	No	Alt text for the tagged-PDF /Figure /Alt. Auto-generated when omitted.
`encrypt`	No	Encrypt at build time (AES-128 default / AES-256) and KEEP the AcroForm — unlike encrypt_pdf, which rebuilds the page tree. Exclusive with pdfA. Randomised output, never cached.
`margins`	No	Margins in points, all four required (0–200). Default 45 / 36 / 35 / 36.
`markers`	No	Draw point markers on line series. Default false.
`compress`	No	FlateDecode the streams (smaller file, different bytes; PDF/A unaffected, XMP stays plain). Default false.
`metadata`	No	/Info (+ XMP under PDF/A): author, subject, keywords, /Trapped.
`pageSize`	No	Portrait page preset (points): A4 595.28×841.89 (default), Letter 612×792, Legal 612×1008, A3 841.89×1190.55, Tabloid 792×1224. print.* boxes must fit it.
`chartType`	Yes	Chart kind. 'pie'/'donut' use exactly one series; 'bar'/'barH'/'stackedBar'/'stackedBarH'/'line'/'area'/'scatter' support multiple series. 'scatter' requires xValues on every series and a positional xAxis.type ('linear' or 'time').
`categories`	No	Category / slice labels (x-axis). Defaults to 1-based indices when omitted.
`dataLabels`	No	Per-point value labels: true for defaults, or an object to format them.
`embedFonts`	No	Embed Noto Sans Latin instead of the viewer base-14 Helvetica. REQUIRED for a valid PDF/A claim (ISO 19005 §6.2.11.4.1) and for strict=true; adds ~0.3 MiB.
`outputMode`	No	Either 'base64' (returns the PDF inline) or 'file' (writes into the PDFNATIVE_MCP_OUTPUT_DIR sandbox).	base64
`outputPath`	No	Required when outputMode='file'. Relative path inside the sandbox; must end with .pdf.
`labelStride`	No	Draw every Nth category label. Default: automatic (measured non-overlap); 1 draws every label.
`creationDate`	No	ISO-8601 instant for /CreationDate (+ XMP). Pin it for byte-identical output across calls (same host TZ); omitted = wall clock, so every call differs.
`outputIntent`	No	Custom PDF/A OutputIntent: an RGB ICC profile + condition strings replacing the built-in sRGB intent (CMYK rejected).
`labelRotation`	No	Rotate category labels counter-clockwise by this many degrees (disables the automatic stride).
`footerTemplate`	No	Running footer on every page. Replaces the default footer: footerText is then ignored and page numbers appear only via {page}/{pages}.
`headerTemplate`	No	Running header on every page (left / center / right zones); reserves 15 pt.
`includeDiagnostics`	No	Return the PDF/A diagnostics raised while building as `diagnostics[]` (possibly empty).

Output Schema

TableJSON Schema

Name	Required	Description
`mode`	Yes
`summary`	No	Tool-specific summary, when produced.
`filePath`	No	Sandboxed absolute path (file mode).
`sizeBytes`	Yes
`diagnostics`	No	PDF/A diagnostics (when includeDiagnostics=true).

Schema Changelog

Changes observed during successful MCP inspections.

Changed29 schema fields changedAug 24, 2026

addedInput schema / properties / axis / properties / scale

Added value: +{
+  "description": "Value-axis scale. 'log' requires strictly positive values and is not available for stacked charts.",
+  "enum": [
+    "linear",
+    "log"
+  ],
+  "type": "string"
+}

addedInput schema / properties / axis2

Added value: +{
+  "additionalProperties": false,
+  "description": "Secondary RIGHT value axis (drawn only when a series sets yAxis:'right').",
+  "properties": {
+    "scale": {
+      "enum": [
+        "linear",
+        "log"
+      ],
+      "type": "string"
+    },
+    "ticks": {
+      "maximum": 20,
+      "minimum": 2,
+      "type": "integer"
+    },
+    "yMax": {
+      "type": "number"
+    },
+    "yMin": {
+      "type": "number"
+    }
+  },
+  "type": "object"
+}

changedInput schema / properties / chartType / description

Previous value: -"Chart kind. 'pie'/'donut' use exactly one series; 'bar'/'barH'/'line' support multiple series."New value: +"Chart kind. 'pie'/'donut' use exactly one series; 'bar'/'barH'/'stackedBar'/'stackedBarH'/'line'/'area'/'scatter' support multiple series. 'scatter' requires xValues on every series and a positional xAxis.type ('linear' or 'time')."

changedInput schema / properties / chartType / enum

Previous value: -[
-  "bar",
-  "barH",
-  "line",
-  "pie",
-  "donut"
-]New value: +[
+  "bar",
+  "barH",
+  "stackedBar",
+  "stackedBarH",
+  "line",
+  "area",
+  "scatter",
+  "pie",
+  "donut"
+]

addedInput schema / properties / compress

Added value: +{
+  "description": "FlateDecode the streams (smaller file, different bytes; PDF/A unaffected, XMP stays plain). Default false.",
+  "type": "boolean"
+}

addedInput schema / properties / creationDate

Added value: +{
+  "description": "ISO-8601 instant for /CreationDate (+ XMP). Pin it for byte-identical output across calls (same host TZ); omitted = wall clock, so every call differs.",
+  "format": "date-time",
+  "type": "string"
+}

addedInput schema / properties / dataLabels

Added value: +{
+  "description": "Per-point value labels: true for defaults, or an object to format them.",
+  "oneOf": [
+    {
+      "type": "boolean"
+    },
+    {
+      "additionalProperties": false,
+      "properties": {
+        "decimals": {
+          "maximum": 6,
+          "minimum": 0,
+          "type": "integer"
+        },
+        "prefix": {
+          "maxLength": 16,
+          "type": "string"
+        },
+        "suffix": {
+          "maxLength": 16,
+          "type": "string"
+        }
+      },
+      "type": "object"
+    }
+  ]
+}

addedInput schema / properties / debug

Added value: +{
+  "description": "Draw margin / block / cell guide rectangles (unmarked content — not for PDF/UA output). Geometry unchanged. Default false.",
+  "type": "boolean"
+}

addedInput schema / properties / embedFonts

Added value: +{
+  "default": false,
+  "description": "Embed Noto Sans Latin instead of the viewer base-14 Helvetica. REQUIRED for a valid PDF/A claim (ISO 19005 §6.2.11.4.1) and for strict=true; adds ~0.3 MiB.",
+  "type": "boolean"
+}

addedInput schema / properties / encrypt

Added value: +{
+  "additionalProperties": false,
+  "description": "Encrypt at build time (AES-128 default / AES-256) and KEEP the AcroForm — unlike encrypt_pdf, which rebuilds the page tree. Exclusive with pdfA. Randomised output, never cached.",
+  "properties": {
+    "algorithm": {
+      "default": "aes128",
+      "description": "aes128 (V4/R4, widest compatibility) or aes256 (V5/R6).",
+      "enum": [
+        "aes128",
+        "aes256"
+      ],
+      "type": "string"
+    },
+    "ownerPassword": {
+      "description": "Owner password (full access).",
+      "maxLength": 4096,
+      "minLength": 1,
+      "type": "string"
+    },
+    "permissions": {
+      "additionalProperties": false,
+      "description": "Permission flags; each defaults to allowed.",
+      "properties": {
+        "copy": {
+          "type": "boolean"
+        },
+        "extractText": {
+          "type": "boolean"
+        },
+        "modify": {
+          "type": "boolean"
+        },
+        "print": {
+          "type": "boolean"
+        }
+      },
+      "type": "object"
+    },
+    "userPassword": {
+      "description": "Open password; omitted/empty = opens without a prompt.",
+      "maxLength": 4096,
+      "type": "string"
+    }
+  },
+  "required": [
+    "ownerPassword"
+  ],
+  "type": "object"
+}

addedInput schema / properties / footerTemplate

Added value: +{
+  "additionalProperties": false,
+  "description": "Running footer on every page. Replaces the default footer: footerText is then ignored and page numbers appear only via {page}/{pages}.",
+  "properties": {
+    "center": {
+      "description": "Placeholders: {page} {pages} {title} {date} (build-day wall clock, not creationDate).",
+      "maxLength": 200,
+      "type": "string"
+    },
+    "color": {
+      "description": "Hex colour.",
+      "pattern": "^#[0-9a-fA-F]{6}$",
+      "type": "string"
+    },
+    "fontSize": {
+      "description": "Default 7.",
+      "maximum": 14,
+      "minimum": 6,
+      "type": "number"
+    },
+    "left": {
+      "description": "Placeholders: {page} {pages} {title} {date} (build-day wall clock, not creationDate).",
+      "maxLength": 200,
+      "type": "string"
+    },
+    "right": {
+      "description": "Placeholders: {page} {pages} {title} {date} (build-day wall clock, not creationDate).",
+      "maxLength": 200,
+      "type": "string"
+    }
+  },
+  "type": "object"
+}

addedInput schema / properties / headerTemplate

Added value: +{
+  "additionalProperties": false,
+  "description": "Running header on every page (left / center / right zones); reserves 15 pt.",
+  "properties": {
+    "center": {
+      "description": "Placeholders: {page} {pages} {title} {date} (build-day wall clock, not creationDate).",
+      "maxLength": 200,
+      "type": "string"
+    },
+    "color": {
+      "description": "Hex colour.",
+      "pattern": "^#[0-9a-fA-F]{6}$",
+      "type": "string"
+    },
+    "fontSize": {
+      "description": "Default 7.",
+      "maximum": 14,
+      "minimum": 6,
+      "type": "number"
+    },
+    "left": {
+      "description": "Placeholders: {page} {pages} {title} {date} (build-day wall clock, not creationDate).",
+      "maxLength": 200,
+      "type": "string"
+    },
+    "right": {
+      "description": "Placeholders: {page} {pages} {title} {date} (build-day wall clock, not creationDate).",
+      "maxLength": 200,
+      "type": "string"
+    }
+  },
+  "type": "object"
+}

addedInput schema / properties / includeDiagnostics

Added value: +{
+  "default": false,
+  "description": "Return the PDF/A diagnostics raised while building as `diagnostics[]` (possibly empty).",
+  "type": "boolean"
+}

addedInput schema / properties / labelRotation

Added value: +{
+  "description": "Rotate category labels counter-clockwise by this many degrees (disables the automatic stride).",
+  "maximum": 90,
+  "minimum": 0,
+  "type": "number"
+}

addedInput schema / properties / labelStride

Added value: +{
+  "description": "Draw every Nth category label. Default: automatic (measured non-overlap); 1 draws every label.",
+  "maximum": 1000,
+  "minimum": 1,
+  "type": "integer"
+}

addedInput schema / properties / margins

Added value: +{
+  "additionalProperties": false,
+  "description": "Margins in points, all four required (0–200). Default 45 / 36 / 35 / 36.",
+  "properties": {
+    "bottom": {
+      "maximum": 200,
+      "minimum": 0,
+      "type": "number"
+    },
+    "left": {
+      "maximum": 200,
+      "minimum": 0,
+      "type": "number"
+    },
+    "right": {
+      "maximum": 200,
+      "minimum": 0,
+      "type": "number"
+    },
+    "top": {
+      "maximum": 200,
+      "minimum": 0,
+      "type": "number"
+    }
+  },
+  "required": [
+    "top",
+    "right",
+    "bottom",
+    "left"
+  ],
+  "type": "object"
+}

addedInput schema / properties / metadata

Added value: +{
+  "additionalProperties": false,
+  "description": "/Info (+ XMP under PDF/A): author, subject, keywords, /Trapped.",
+  "properties": {
+    "author": {
+      "maxLength": 500,
+      "type": "string"
+    },
+    "keywords": {
+      "maxLength": 1000,
+      "type": "string"
+    },
+    "subject": {
+      "maxLength": 1000,
+      "type": "string"
+    },
+    "trapped": {
+      "description": "/Trapped print flag.",
+      "enum": [
+        "True",
+        "False",
+        "Unknown"
+      ],
+      "type": "string"
+    }
+  },
+  "type": "object"
+}

addedInput schema / properties / outputIntent

Added value: +{
+  "additionalProperties": false,
+  "description": "Custom PDF/A OutputIntent: an RGB ICC profile + condition strings replacing the built-in sRGB intent (CMYK rejected).",
+  "properties": {
+    "iccProfileBase64": {
+      "description": "ICC profile bytes, base64 (RGB, ≤ 8 MiB).",
+      "maxLength": 11000000,
+      "minLength": 1,
+      "type": "string"
+    },
+    "info": {
+      "maxLength": 500,
+      "type": "string"
+    },
+    "outputCondition": {
+      "maxLength": 200,
+      "type": "string"
+    },
+    "outputConditionIdentifier": {
+      "description": "e.g. \"sRGB IEC61966-2.1\".",
+      "maxLength": 200,
+      "minLength": 1,
+      "type": "string"
+    },
+    "registryName": {
+      "description": "Default \"http://www.color.org\".",
+      "maxLength": 200,
+      "type": "string"
+    }
+  },
+  "required": [
+    "iccProfileBase64",
+    "outputConditionIdentifier"
+  ],
+  "type": "object"
+}

addedInput schema / properties / pageSize

Added value: +{
+  "description": "Portrait page preset (points): A4 595.28×841.89 (default), Letter 612×792, Legal 612×1008, A3 841.89×1190.55, Tabloid 792×1224. print.* boxes must fit it.",
+  "enum": [
+    "A4",
+    "Letter",
+    "Legal",
+    "A3",
+    "Tabloid"
+  ],
+  "type": "string"
+}

changedInput schema / properties / pdfA / description

Previous value: -"Optional PDF/A conformance level (powered by pdfnative v1.2). Use 'pdfa1b' for archival of simple text+images, 'pdfa2b'/'pdfa2u' for richer content (2u guarantees Unicode mapping), 'pdfa3b' when embedding source attachments (Factur-X / ZUGFeRD). Mutually exclusive with PDF encryption. See docs/guides/PDFA.md."New value: +"PDF/A level: pdfa1b (simple text+images), pdfa2b/pdfa2u (richer; 2u = Unicode mapping), pdfa3b (attachments / Factur-X). Pair with embedFonts=true for a valid claim. Exclusive with encryption. See docs/guides/PDFA.md."

addedInput schema / properties / print

Added value: +{
+  "additionalProperties": false,
+  "description": "Print production (ISO 32000-1 §14.11): page boxes, `bleed` shorthand (TrimBox = MediaBox inset), crop/registration marks outside the TrimBox, /UserUnit for large formats (PDF 1.7; not under pdfa1b). See docs/guides/PRINT.md.",
+  "properties": {
+    "artBox": {
+      "description": "[x0, y0, x1, y1] in points, origin bottom-left, inside the MediaBox.",
+      "items": {
+        "type": "number"
+      },
+      "maxItems": 4,
+      "minItems": 4,
+      "type": "array"
+    },
+    "bleed": {
+      "description": "Bleed in points (8.5 = 3 mm); sets TrimBox = MediaBox inset. Exclusive with trimBox.",
+      "exclusiveMinimum": 0,
+      "maximum": 200,
+      "type": "number"
+    },
+    "bleedBox": {
+      "description": "[x0, y0, x1, y1] in points, origin bottom-left, inside the MediaBox.",
+      "items": {
+        "type": "number"
+      },
+      "maxItems": 4,
+      "minItems": 4,
+      "type": "array"
+    },
+    "cropBox": {
+      "description": "[x0, y0, x1, y1] in points, origin bottom-left, inside the MediaBox.",
+      "items": {
+        "type": "number"
+      },
+      "maxItems": 4,
+      "minItems": 4,
+      "type": "array"
+    },
+    "marks": {
+      "description": "Printer's marks (needs bleed or trimBox): true for defaults, or an object.",
+      "oneOf": [
+        {
+          "type": "boolean"
+        },
+        {
+          "additionalProperties": false,
+          "properties": {
+            "crop": {
+              "description": "Corner crop (trim) marks. Default true.",
+              "type": "boolean"
+            },
+            "length": {
+              "description": "Mark length in points. Default 14.",
+              "maximum": 100,
+              "minimum": 1,
+              "type": "number"
+            },
+            "offset": {
+              "description": "Gap between TrimBox and marks in points. Default 5.",
+              "maximum": 100,
+              "minimum": 0,
+              "type": "number"
+            },
+            "registration": {
+              "description": "Edge-midpoint registration targets. Default true.",
+              "type": "boolean"
+            },
+            "weight": {
+              "description": "Stroke width in points. Default 0.25.",
+              "maximum": 5,
+              "minimum": 0.05,
+              "type": "number"
+            }
+          },
+          "type": "object"
+        }
+      ]
+    },
+    "trimBox": {
+      "description": "[x0, y0, x1, y1] in points, origin bottom-left, inside the MediaBox.",
+      "items": {
+        "type": "number"
+      },
+      "maxItems": 4,
+      "minItems": 4,
+      "type": "array"
+    },
+    "userUnit": {
+      "description": "/UserUnit (multiples of 1/72 in) for pages over 14400 pt. Rejected under pdfa1b.",
+      "maximum": 75000,
+      "minimum": 1,
+      "type": "number"
+    }
+  },
+  "type": "object"
+}

addedInput schema / properties / series / items / properties / xValues

Added value: +{
+  "description": "Per-point x positions (same length as values) for scatter charts and for line/area charts with xAxis.type 'linear' or 'time'.",
+  "items": {
+    "description": "Positional x value: a number (linear axis) or an ISO-8601 date / epoch milliseconds (time axis).",
+    "maxLength": 64,
+    "type": [
+      "number",
+      "string"
+    ]
+  },
+  "maxItems": 1000,
+  "minItems": 1,
+  "type": "array"
+}

addedInput schema / properties / series / items / properties / yAxis

Added value: +{
+  "description": "Bind the series to the left (default) or the secondary right value axis (cartesian charts only; configure its range with 'axis2').",
+  "enum": [
+    "left",
+    "right"
+  ],
+  "type": "string"
+}

addedInput schema / properties / strict

Added value: +{
+  "default": false,
+  "description": "Fail with PDF_A_COMPLIANCE_VIOLATION instead of producing a non-conformant PDF/A file (e.g. PDFA_NO_FONT_ENTRIES without embedFonts). Pair with embedFonts=true.",
+  "type": "boolean"
+}

addedInput schema / properties / xAxis

Added value: +{
+  "additionalProperties": false,
+  "description": "Horizontal axis. 'category' (default) positions points by index; 'linear' / 'time' position them by series xValues (line/area/scatter only). Time ticks are UTC-deterministic.",
+  "properties": {
+    "grid": {
+      "description": "Draw vertical gridlines.",
+      "type": "boolean"
+    },
+    "max": {
+      "description": "Axis maximum (number, or ISO-8601 / epoch ms for time axes).",
+      "maxLength": 64,
+      "type": [
+        "number",
+        "string"
+      ]
+    },
+    "min": {
+      "description": "Axis minimum (number, or ISO-8601 / epoch ms for time axes).",
+      "maxLength": 64,
+      "type": [
+        "number",
+        "string"
+      ]
+    },
+    "ticks": {
+      "maximum": 20,
+      "minimum": 2,
+      "type": "integer"
+    },
+    "type": {
+      "enum": [
+        "category",
+        "linear",
+        "time"
+      ],
+      "type": "string"
+    }
+  },
+  "type": "object"
+}

changedOutput schema / description

Previous value: -"Structured result of a PDF-producing tool. In base64 mode the PDF bytes are delivered out-of-band as an embedded `resource` content block (data: URI), NOT duplicated here, to keep responses token-frugal. In file mode `filePath` is the sandboxed absolute path."New value: +"Result of a PDF-producing tool. base64 mode: the PDF arrives as an embedded `resource` content block (not duplicated here); file mode: `filePath`."

addedOutput schema / properties / diagnostics

Added value: +{
+  "description": "PDF/A diagnostics (when includeDiagnostics=true).",
+  "items": {
+    "additionalProperties": false,
+    "properties": {
+      "code": {
+        "type": "string"
+      },
+      "message": {
+        "type": "string"
+      },
+      "severity": {
+        "enum": [
+          "warning"
+        ],
+        "type": "string"
+      }
+    },
+    "required": [
+      "code",
+      "message",
+      "severity"
+    ],
+    "type": "object"
+  },
+  "type": "array"
+}

changedOutput schema / properties / filePath / description

Previous value: -"Absolute sandboxed file path (when mode='file')."New value: +"Sandboxed absolute path (file mode)."

addedOutput schema / properties / summary

Added value: +{
+  "additionalProperties": true,
+  "description": "Tool-specific summary, when produced.",
+  "type": "object"
+}

Addedv1.6.0Jul 22, 2026

TDQS

A3.9/5.0

Behavior4/5

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

Annotations already declare idempotentHint=true and destructiveHint=false, so safety is covered. The description adds valuable behavioral context beyond that: output is a single-page PDF with pure vector paths, pie/donut require exactly one series, errors surface as CHART_ERROR, and PDF/A compliance requires embedFonts. This is strong but not exhaustive; e.g., it doesn't mention default random output unless creationDate is pinned, though the schema does.

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?

The description is a single compact paragraph that packs a lot of feature detail without fluff. It front-loads the core value proposition (native vector chart) and then lists constraints and notable behaviors. It earns 4, not 5, because the dense wall of text could be structured more clearly for an agent scanning for supported chart types or key restrictions.

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

Completeness4/5

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

For a tool with 35 parameters, the description is nearly complete: it covers chart types, vector guarantee, multi-series, axes, pie/donut constraint, error code, routing to generate_basic_pdf, and PDF/A pairing. The output schema exists, so describing return values isn't necessary. It slightly lacks a quick statement about expected output format (base64 vs file) or the default one-page document, but the schema covers the outputMode parameter, so this is a minor gap.

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 the baseline is 3. The description does add some high-level semantics like 'per-series xValues with xAxis.type linear|time' and 'Pie/donut take exactly one series', but these are also repeated in the schema. No significant meaning is added beyond what the schema already documents, so 3 is appropriate.

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 ('Add') and resource ('native vector chart') and enumerates the supported chart types and features. It is clearly distinct from siblings like add_table or embed_image, but it does not explicitly name a sibling tool it is not, so it stops short of a 5.

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?

The description gives a clear routing rule: 'Inside a longer document use a "chart" block in generate_basic_pdf.' This tells the agent when not to use add_chart. However, it doesn't explicitly state when to prefer this tool over other chart-capable paths or give a fuller when-to-use/when-not-to-use comparison, so it doesn't reach 5.

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