colour_cardLook up a named colour and return its hex, archive, provenance, and cultural notes.
| Name | Required | Description | Default |
|---|---|---|---|
| name | No | Colour name e.g. 'Prussian Blue' or 'Ottoman Carbon Ink' | |
| slug | No | Stable colour slug from archive_search e.g. 'keats:keats-s-lung' -- preferred over name for reliable retrieval |
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
Changes observed during successful MCP inspections.
Output 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"
+}Output schema / (root)Previous value: -{
- "properties": {
- "error": {
- "type": "string"
- },
- "ok": {
- "type": "boolean"
- },
- "result": {
- "type": [
- "object",
- "array",
- "string",
- "null"
- ]
- }
- },
- "type": "object"
-}New value: +nullDoes the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The readOnlyHint annotation already signals safe read-only behavior, and the description adds value by specifying the exact kind of data returned (hex, archive, provenance, cultural notes). It does not introduce contradictions or hidden side effects, making the behavior clear for a lookup tool.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single, well-structured sentence that front-loads the primary action and outcome. It contains no filler or repetition, earning its place efficiently.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the presence of an output schema, a readOnlyHint annotation, and detailed parameter descriptions, the concise description is largely sufficient. It could benefit from a note about fallback behavior when a name is not found or when to prefer slug over name, but the current coverage is adequate for straightforward usage.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The input schema provides 100% coverage with clear descriptions for both parameters (name and slug), including the suggestion that slug is preferred. The tool description adds no additional parameter-level meaning beyond the schema, so the baseline score of 3 is appropriate.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description uses a specific verb ('look up') and resource ('named colour') and lists the return contents (hex, archive, provenance, cultural notes). It distinguishes itself from colour_* siblings by focusing on details by name, though it doesn't explicitly differentiate from similar lookup tools like colour_passport.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description implies when to use the tool ('when you have a named colour'), but it does not provide explicit guidance on when to use it vs alternatives or mention prerequisites like using archive_search to obtain a slug. No exclusions or alternatives are noted.
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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