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blocklens-mcp-server

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by blocklens

render_chart

Render Bitcoin on-chain analytics charts as PNG images. Visualize single or multiple metrics with customizable templates, formulas, and axes.

Instructions

Render a Bitcoin on-chain analytics chart as a PNG image. Supports single metrics, multiple metrics, templates, computed formulas, and full customization.

Use this when the user asks to "show", "chart", "plot", "graph", or "visualize" any metric.

Smart defaults: just provide metric IDs and you get a beautiful chart. Customize with optional params.

Supports custom Y-axes with vertical zones (stack volume below price), domain clamping, reference lines, reference areas, and computed formula series.

IMPORTANT — Multi-axis guidance for different units: When combining metrics with different units (e.g., BTC supply + USD price, or a dimensionless ratio + USD), ALWAYS place them on separate Y-axes. Otherwise one metric will appear as a flat line near zero due to scale mismatch. Use list_metrics to check the "unit" field and assign metrics with different units to different axes (left vs right).

Examples:

  • Simple: render_chart({ metric: "price" })

  • Multi-metric: render_chart({ metrics: ["lth_supply", "sth_supply"], days: 730, style: "area" })

  • Template: render_chart({ template: "mvrv_ratio" })

  • Custom: render_chart({ metrics: [{ id: "price", axis: "right" }, { id: "lth_mvrv", axis: "left" }], days: 365, title: "Price vs MVRV" })

  • Multi-unit (separate axes): render_chart({ metrics: [{ id: "lth_supply", axis: "left" }, { id: "price", axis: "right" }], days: 365 })

  • Vertical zones: render_chart({ metrics: [{ id: "price", y_axis_id: "ax-p" }, { id: "volume", y_axis_id: "ax-v", style: "bar" }], y_axes: [{ id: "ax-p", side: "right", range: [20, 100] }, { id: "ax-v", side: "left", range: [0, 20] }] })

  • Reference line: render_chart({ metric: "lth_mvrv", reference_lines: [{ y: 3.5, label: "Overheated", stroke: "#ef4444", dash: "3 3" }] })

  • Reference area: render_chart({ metric: "lth_mvrv", reference_areas: [{ y1: 0, y2: 0.85, label: "Undervalued", fill: "#22c55e", fill_opacity: 0.15 }] })

  • Formula (ratio): render_chart({ metrics: [{ id: "lth_supply" }, { id: "sth_supply" }], formulas: [{ expression: "m1 / m2", label: "LTH/STH Ratio", color: "#f59e0b" }], days: 365 })

  • Formula on separate axis: render_chart({ metrics: [{ id: "lth_supply", axis: "left" }, { id: "sth_supply", axis: "left" }], formulas: [{ expression: "m1 / m2", label: "LTH/STH Ratio", y_axis_id: "ax-r" }], y_axes: [{ id: "ax-r", side: "right" }], days: 365 })

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
daysNoDays of history (default: 365)
scaleNoY-axis scalelinear
styleNoDefault chart style for all metrics
themeNoColor theme: light or darklight
titleNoChart title (auto-generated if omitted)
widthNoImage width in pixels
formatNoOutput format: png (image) or json (metadata)png
heightNoImage height in pixels
metricNoSingle metric ID (e.g., "price", "lth_supply", "lth_mvrv"). Use list_metrics to discover IDs.
y_axesNoCustom Y-axes with vertical zones. Use range to stack axes (e.g. volume [0,20], price [20,100]). Use domain_min/domain_max to clamp axis bounds.
metricsNoMultiple metrics. Pass as string array ["price", "lth_supply"] for simple, or objects for customization.
overlayNoAdd BTC price overlay (subtle dashed line)
end_dateNoEnd date (YYYY-MM-DD). Defaults to today.
formulasNoComputed series derived from metric data. Formulas reference metrics by position (m1, m2, ...) and support arithmetic (+, -, *, /). Use together with metrics to add derived indicators.
templateNoChart template ID. Templates: price, price_volume, market_cap, holder_supply, mvrv_ratio, realized_price, realized_cap, unrealized_pl, realized_pl, sopr, block_height, realized_volatility, coindays_destroyed, dormancy_flow, liveliness
start_dateNoStart date (YYYY-MM-DD). Overrides days.
reference_areasNoShaded reference zones between two Y values. Example: highlight when MVRV < 0.85
reference_linesNoHorizontal reference lines on the chart
Behavior4/5

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 discloses key behaviors including multi-axis handling, vertical zones, domain clamping, and the critical pitfall of flat lines when mixing units on the same axis. It also mentions 'smart defaults' and provides concrete examples. It lacks details on error handling or rate limits, but the main operational quirks are well covered.

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 lengthy but effective. It is front-loaded with a clear summary, followed by usage triggers and 'IMPORTANT' guidance, then well-organized examples covering each feature. While it is verbose, every sentence provides substantive value, and the examples serve as compact parameter documentation.

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?

Given 18 parameters, nested structures, and no output schema, this description is exceptionally complete. It covers all major capabilities, provides caveats for unit scaling, and demonstrates usage for each feature category. The agent can confidently construct complex chart requests based on the examples and guidance.

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

Parameters5/5

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

Schema description coverage is 100%, giving a baseline of 3. The description goes well beyond by providing multiple examples that illustrate parameter combinations (e.g., y_axes, reference_lines, formulas) and explains the 'm1/m2' formula syntax. It adds practical semantic meaning, such as using range [0,20] for stacking axes, which is not fully apparent from the schema alone.

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?

The description states exactly what the tool does: 'Render a Bitcoin on-chain analytics chart as a PNG image.' It clearly distinguishes from sibling data-fetching tools by focusing on visualization with verbs like 'chart' and 'plot', and mentions specific capabilities (templates, formulas, customization).

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 provides explicit usage triggers: 'Use this when the user asks to show, chart, plot, graph, or visualize any metric.' It gives extensive examples and multi-axis guidance, though it does not explicitly name alternative tools for data retrieval. The context is clear enough to decide when to use this tool versus siblings.

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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