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RFC 0008: Skills Extension

RFC 0008: Skills Extension

  • Status: Implemented
  • Author(s): AltairaLabs Team
  • Created: 2026-02-21
  • Updated: 2026-02-21
  • Related Issues: N/A

Summary

Extend the PromptPack specification with a skills field for progressive-disclosure knowledge loading, following the AgentSkills.io standard. The extension adds a top-level skills array that declares external skill sources (file paths, package references, or inline definitions) and a skills string field on WorkflowState for directory-scoped skill filtering within workflow states.

Motivation

As prompt packs grow in complexity, agents need access to domain-specific knowledge that goes beyond what fits in a system template. Skills represent modular, reusable knowledge units that can be loaded on demand — instructions for specific tasks, domain expertise, or behavioral patterns that an agent activates when relevant.

Current Limitations

Without a skills mechanism, developers must:

  • Embed all domain knowledge directly in system templates, leading to bloated prompts
  • Manually manage which knowledge is available in which context
  • Duplicate instructions across prompts when multiple prompts need the same expertise
  • Hardcode knowledge loading in runtime code, breaking PromptPack’s portability promise

This leads to:

  • Prompt bloat — system templates grow unwieldy as domain knowledge accumulates
  • Poor discoverability — no standard way to declare what knowledge an agent can access
  • Tight coupling — knowledge management logic lives in runtime code, not the pack
  • No progressive disclosure — all knowledge loads upfront rather than on demand

Goals

  • Allow authors to declare skill sources (file paths, packages, or inline definitions) within a pack
  • Enable directory-scoped skill filtering within workflow states
  • Support progressive-disclosure loading where skills activate on demand
  • Maintain full backward compatibility with existing packs
  • Follow the AgentSkills.io standard for skill definition and discovery

Non-Goals

  • Define skill execution semantics (how skills are interpreted at runtime)
  • Specify skill resolution protocols (how packages are fetched)
  • Replace or subsume the existing agents section — skills complement agents
  • Define skill versioning or dependency resolution

Detailed Design

Core Concept

A skill is a named, self-contained unit of knowledge or instructions that an agent can load on demand. Skills can be sourced from:

  1. File paths — local directories or files containing skill definitions
  2. Package references — external packages following the AgentSkills.io standard
  3. Inline definitions — skills defined directly in the pack with name, description, and instructions

Schema Changes

New Top-Level Field: skills

{
  "skills": {
    "type": "array",
    "description": "Skill sources for progressive-disclosure knowledge loading. Each entry is either a string (path or package reference) or an object with detailed configuration.",
    "items": {
      "$ref": "#/$defs/SkillSource"
    }
  }
}

New Definition: SkillSource

{
  "SkillSource": {
    "oneOf": [
      {
        "type": "string",
        "description": "Path to a skill directory/file or a package reference (e.g., './skills', '@acme/billing-skills')."
      },
      {
        "$ref": "#/$defs/SkillPathSource"
      },
      {
        "$ref": "#/$defs/InlineSkill"
      }
    ]
  }
}

New Definition: SkillPathSource

{
  "SkillPathSource": {
    "type": "object",
    "description": "A skill source with a path and optional preload configuration.",
    "required": ["path"],
    "additionalProperties": false,
    "properties": {
      "path": {
        "type": "string",
        "description": "Path to a skill directory, file, or package reference."
      },
      "preload": {
        "type": "boolean",
        "description": "If true, load this skill source eagerly at pack initialization rather than on demand.",
        "default": false
      }
    }
  }
}

New Definition: InlineSkill

{
  "InlineSkill": {
    "type": "object",
    "description": "A skill defined inline within the pack. Useful for small, pack-specific skills that don't warrant a separate file.",
    "required": ["name", "description", "instructions"],
    "additionalProperties": false,
    "properties": {
      "name": {
        "type": "string",
        "description": "Human-readable name for this skill.",
        "minLength": 1
      },
      "description": {
        "type": "string",
        "description": "Brief description of what this skill provides.",
        "minLength": 1
      },
      "instructions": {
        "type": "string",
        "description": "The skill's instructions or knowledge content. Loaded into the agent's context when the skill is activated.",
        "minLength": 1
      }
    }
  }
}

New Field on WorkflowState: skills

{
  "skills": {
    "type": "string",
    "description": "Skill filter for this workflow state. A path to a skill directory/file that scopes which skills are available in this state, or the literal 'none' to disable skills."
  }
}

How Skills Work

  1. Declaration: The pack’s top-level skills array declares available skill sources. These can be file paths, package references, or inline definitions.

  2. Resolution: At runtime, the runtime resolves each skill source:

    • Strings are treated as paths or package references
    • SkillPathSource objects provide a path with optional eager loading (preload: true)
    • InlineSkill objects contain the skill definition directly

  3. Activation: Skills are loaded progressively — by default, they activate on demand when relevant to the current context. Skills with preload: true load eagerly.

  4. State Scoping: When a WorkflowState declares a skills field, it filters which skills are available in that state. The value "none" disables all skills for that state.

Specification Impact

  • The skills field is added to the top-level pack schema as an optional property
  • The SkillSource, SkillPathSource, and InlineSkill definitions are added to $defs
  • A skills string field is added to WorkflowState
  • All existing fields and definitions remain unchanged
  • Packs without skills are unaffected

Validation Rules

  1. Inline skill uniqueness: Inline skill name values should be unique within the skills array
  2. Path validation: File paths in SkillPathSource and string entries should point to valid locations (runtime validation)
  3. WorkflowState skills: The skills field on a workflow state must be either a valid path/reference or the literal string "none"
  4. Backward compatibility: The skills field is optional; existing packs without it remain valid

Examples

Example 1: File Path Skills

{
  "id": "customer-support",
  "name": "Customer Support Pack",
  "version": "1.3.1",
  "skills": [
    "./skills/billing",
    "./skills/technical-support"
  ],
  "prompts": { "..." : "..." }
}

Example 2: Mixed Skill Sources

{
  "id": "enterprise-support",
  "name": "Enterprise Support Pack",
  "version": "1.3.1",
  "skills": [
    "./skills/common",
    { "path": "./skills/compliance", "preload": true },
    {
      "name": "escalation-protocol",
      "description": "Steps for escalating unresolved customer issues",
      "instructions": "When a customer issue cannot be resolved within 3 exchanges:\n1. Acknowledge the complexity\n2. Collect case details\n3. Create an escalation ticket\n4. Provide the ticket reference to the customer"
    }
  ],
  "prompts": { "..." : "..." }
}

Example 3: Workflow State Skill Scoping

{
  "id": "support-workflow",
  "name": "Support Workflow",
  "version": "1.3.1",
  "skills": [
    "./skills/billing",
    "./skills/technical",
    "./skills/general"
  ],
  "workflow": {
    "version": 1,
    "entry": "triage",
    "states": {
      "triage": {
        "prompt_task": "triage",
        "on_event": { "billing": "billing_state", "technical": "tech_state" },
        "skills": "./skills/general"
      },
      "billing_state": {
        "prompt_task": "billing",
        "on_event": { "resolved": "closing" },
        "skills": "./skills/billing"
      },
      "tech_state": {
        "prompt_task": "technical",
        "on_event": { "resolved": "closing" },
        "skills": "./skills/technical"
      },
      "closing": {
        "prompt_task": "closing",
        "on_event": {},
        "skills": "none"
      }
    }
  },
  "prompts": { "..." : "..." }
}

Drawbacks

Minimal Runtime Specification

The design intentionally leaves skill resolution and execution to runtimes. This provides flexibility but means different runtimes may handle skills differently.

Mitigation: The AgentSkills.io standard provides a reference implementation. PromptKit will serve as the canonical runtime.

Path-Based References

File paths are environment-dependent. A skill path that works locally may not resolve in a cloud deployment.

Mitigation: Package references (@scope/package) provide a portable alternative. Runtimes can also remap paths during deployment.

Alternatives

Alternative 1: Skills on Each Prompt

Add a skills array directly on each prompt definition.

Rejected: Skills are a pack-level concern — they represent shared domain knowledge. Per-prompt skills would lead to duplication. Workflow state scoping provides per-context filtering when needed.

Alternative 2: Extend the Fragments System

Reuse the existing fragments mechanism for skill content.

Rejected: Fragments are compile-time text substitutions. Skills are runtime knowledge units with progressive disclosure. They serve fundamentally different purposes.

Alternative 3: Embed in Agents Section

Add skills as a property of AgentDef.

Rejected: Skills are orthogonal to agents. A pack can use skills without agents, and vice versa. Coupling them would limit flexibility.

Adoption Strategy

Backward Compatibility

  • Fully backward compatible
  • Requires migration
  • Breaking change

The skills field is entirely optional. Existing packs without it remain valid. Runtimes that don’t support skills ignore the field.

Migration Path

No migration required. Adoption is incremental:

  1. Phase 1: Continue using packs without skills (current behavior)
  2. Phase 2: Add top-level skills with file path references
  3. Phase 3: Use inline skills for small, pack-specific knowledge
  4. Phase 4: Add skills to workflow states for context-scoped filtering

Runtime Support Levels

  • Level 0: Ignore skills field (backward compatible)
  • Level 1: Resolve skill sources and load at startup
  • Level 2: Full progressive-disclosure loading with workflow state scoping

Unresolved Questions

1. Package Reference Format

Should package references follow npm-style (@scope/package) or a custom format? The current design accepts any string, leaving format interpretation to runtimes.

Proposal: Accept any string. Runtimes that support package resolution define their own conventions.

2. Skill Priority and Conflicts

When multiple skill sources provide conflicting instructions, which takes precedence?

Proposal: Last-declared wins (array order matters). Runtimes may provide more sophisticated conflict resolution.

3. Relationship with System Templates

Should skills append to or replace system template content?

Proposal: Skills supplement the system template. The system template defines core behavior; skills provide additional context-specific knowledge.

Future Considerations

Skill Dependencies

Skills that depend on other skills:

{
  "name": "advanced-billing",
  "description": "Advanced billing procedures",
  "instructions": "...",
  "depends_on": ["basic-billing"]
}

Skill Conditions

Conditional skill activation based on runtime state:

{
  "path": "./skills/premium-support",
  "condition": "customer.tier == 'enterprise'"
}

Skill Metrics

Track skill activation frequency and effectiveness via the existing evals/metrics system.

Revision History

  • 2026-02-21: Initial draft

References