Skills are instructional multi-step workflows embedded in a schema. Unlike Prompts (which explain context), Skills instruct — they tell an LLM exactly what to do, step by step. Each skill declares its tool dependencies, defines typed input parameters, and records the model it was tested with.
Skills vs Prompts: Use a Prompt when you want to provide context or explain a domain. Use a Skill when you want to orchestrate a repeatable multi-step workflow that calls specific tools in sequence.
Skill Execution Flow
How a skill is resolved and executed at runtime:
The skill’s content is a template. Placeholders like {{input:tokenSymbol}} are replaced with user-provided values, and {{tool:computeRSI}} references tell the LLM which tool to call at each step.
Defining Skills
Skills are declared in the main export’s skills key. Each entry points to a separate .mjs file:
export const main = {
namespace: 'tradingsignals',
name: 'TradingSignals',
version: '3.0.0',
root: 'https://api.example.com',
tools: {
computeRSI: { /* ... */ },
computeMACD: { /* ... */ }
},
skills: {
'token-technical-analysis': { file: './skills/token-technical-analysis.mjs' }
}
}
Skill Reference Fields
Each key in main.skills is the skill name (must match ^[a-z][a-z0-9-]*$). The value is an object:
| Field | Type | Required | Description |
|---|
file | string | Yes | Path to the .mjs skill file, relative to the schema. Must end in .mjs. |
skill object with the full workflow definition:
const content = `Perform technical analysis of {{input:tokenSymbol}} on {{input:chain}}.
## Step 1: Token Discovery
Use {{tool:searchBySymbol}} to find {{input:tokenSymbol}} on {{input:chain}}.
## Step 2: OHLCV Data
Use {{tool:getRecursiveOhlcvEVM}} for {{input:timeframeDays}}-day candles.
## Step 3: Indicators
Use {{tool:computeRSI}} with period 14.
Use {{tool:computeMACD}} with fast 12, slow 26, signal 9.
## Step 4: Synthesis
Compile findings into BULLISH / BEARISH / NEUTRAL signal.`
export const skill = {
name: 'token-technical-analysis',
version: 'flowmcp-skill/1.0.0',
description: 'Full technical analysis: discovery, OHLCV, indicators, chart, signal summary',
testedWith: 'anthropic/claude-sonnet-4-5-20250929',
requires: {
tools: [
'indicators/tool/searchBySymbol',
'ohlcv/tool/getRecursiveOhlcvEVM',
'tradingsignals/tool/computeRSI',
'tradingsignals/tool/computeMACD'
],
resources: [],
external: [ 'playwright' ]
},
input: [
{ key: 'tokenSymbol', type: 'string', description: 'Token symbol (e.g. WETH)', required: true },
{ key: 'chain', type: 'string', description: 'Blockchain (e.g. ethereum)', required: true },
{ key: 'timeframeDays', type: 'number', description: 'Days of history', required: false }
],
output: 'Structured report with trend, momentum, volatility, chart, and signal summary',
content
}
Skill Object Fields
| Field | Type | Required | Description |
|---|
name | string | Yes | Must match the name in the schema’s skills array entry. |
version | string | Yes | Must be 'flowmcp-skill/1.0.0'. |
description | string | Yes | What this skill does. |
testedWith | string | Yes | Model ID the skill was tested with (e.g. anthropic/claude-sonnet-4-5-20250929). |
requires | object | Yes | Dependencies: tools, resources, and external arrays. |
input | array | No | User-provided input parameters. |
output | string | No | Description of what the skill produces. |
content | string | Yes | The instruction text with placeholders. |
testedWith is required for Skills. Every skill must declare which model it was tested with. This is a key difference from Prompts, which do not require testedWith. The field records accountability — if a skill produces unreliable results, the tested model is the first variable to check.
requires Object
| Field | Type | Description |
|---|
tools | string[] | Tool references this skill uses. Uses the full ID format (namespace/tool/name) for cross-schema references, or plain names for same-schema tools. |
resources | string[] | Resource names this skill reads. Must match names in main.resources. |
external | string[] | External capabilities not provided by the schema (e.g. playwright, puppeteer). For documentation purposes. |
requires.external is Skills-only. Prompts do not have an external field. Use it to document dependencies that exist outside the FlowMCP ecosystem, so consumers know what additional setup is needed.
| Field | Type | Description |
|---|
key | string | Parameter name (camelCase). Referenced in content as {{input:key}}. |
type | string | One of string, number, boolean, or enum. |
description | string | What this input parameter is for. |
required | boolean | Whether the user must provide this value. |
Placeholder Syntax
The content field supports four placeholder types, identical to the Prompts placeholder system:
| Placeholder | Syntax | Resolves To | Example |
|---|
| Tool reference | {{tool:name}} | Tool name from requires.tools | {{tool:computeRSI}} |
| Resource reference | {{resource:name}} | Resource name from requires.resources | {{resource:verifiedContracts}} |
| Skill reference | {{skill:name}} | Another skill in the same schema | {{skill:quick-check}} |
| Input reference | {{input:key}} | User-provided input value | {{input:tokenSymbol}} |
Placeholder Rules
{{tool:x}} — x should be listed in requires.tools{{resource:x}} — x should be listed in requires.resources{{skill:x}} — must reference another skill in the same schema (no circular references){{input:x}} — should match an input[].key
Unresolved placeholders produce validation warnings (not errors), except for {{skill:x}} which must resolve.
Constraints
| Constraint | Value | Rationale |
|---|
| Max skills per schema | 4 | Keep schemas focused |
testedWith | Required | Accountability for non-deterministic workflows |
requires.external | Skills-only | Prompts do not support this field |
| Skill name pattern | ^[a-z][a-z0-9-]*$ | Lowercase with hyphens |
| Skill file extension | .mjs | ES module format |
| Version | flowmcp-skill/1.0.0 | Fixed for v3.0.0 |
| Content | Non-empty string | Must contain instructions |
| No circular references | Via {{skill:x}} | Prevents infinite loops |
Skills vs Prompts Summary
| Aspect | Prompt | Skill |
|---|
| Purpose | Explain context | Instruct step-by-step |
testedWith | Optional | Required |
requires.external | Not available | Available |
| Placeholder system | Same | Same |
| Max per schema | 4 | 4 |
| File format | .mjs | .mjs |
| MCP primitive | Prompts | Prompts |
