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Colour Memory

by app.railway.up.colour-memory-api-production
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Get Colour Metrics and Properties

colour_metrics
Read-only

Returns numeric metrics derived from a single display colour: an estimated light reflectance value (LRV) and band, relative luminance, CIELAB lightness, chroma and hue angle, and Bradford corresponding colours under two standard illuminants. It also lists what a hex cannot support, such as thermal performance or a measured LRV. This is one component of colour_passport. Use colour_passport for a general colour profile; use this only when the user explicitly wants isolated numeric values.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
hex_valYesHex value e.g. '#8B4513'

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault

No arguments

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changed
    • changedOutput schema / (root)
      Previous value: -nullNew value: +{
+  "additionalProperties": true,
+  "description": "Structured JSON response. Shape varies by tool; most return an 'ok' boolean plus a 'result' or 'results' field with the tool's data payload.",
+  "type": "object"
+}
  2. Changed1 schema field changed
    • changedOutput schema / (root)
      Previous value: -{
-  "properties": {
-    "error": {
-      "type": "string"
-    },
-    "ok": {
-      "type": "boolean"
-    },
-    "result": {
-      "type": [
-        "object",
-        "array",
-        "string",
-        "null"
-      ]
-    }
-  },
-  "type": "object"
-}New value: +null
  3. Added

TDQS

A4.5/5.0
Behavior4/5

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

The readOnlyHint annotation already signals safety, and the description adds meaningful behavioral detail: the values are estimated, limited to what a hex can support, and computed under two standard illuminants. It also calls out limitations like thermal performance and measured LRV, which helps an agent set user expectations without contradicting the annotations.

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?

The description is compact, front-loaded with the core purpose, and every sentence earns its place: first states what it returns, then notes its limitations, then routes to the sibling. The detailed list is dense but not padded.

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?

With one parameter, readOnlyHint annotations, and an output schema, the description covers everything needed to invoke the tool correctly: what it computes, what it cannot compute, and when to prefer colour_passport. No critical context 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 the schema already documents hex_val. The description reinforces that the input is a single display colour and notes hex limitations, but it does not add parameter-level details beyond what the schema provides. Baseline 3 is appropriate.

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 begins with a specific action and resource: 'Returns numeric metrics derived from a single display colour' and enumerates exact quantities (LRV, luminance, CIELAB lightness, chroma, hue angle, Bradford corresponding colours). It also explicitly distinguishes itself from colour_passport, so an agent can reliably tell this tool apart from a key sibling 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?

The description gives clear when-to-use guidance: 'Use colour_passport for a general colour profile; use this only when the user explicitly wants isolated numeric values.' This explicitly names the alternative and states the condition that selects this tool, leaving no ambiguity about routing.

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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