Agent Capability Registry
An agent capability registry is the catalog of actions, patterns, and source artifacts an agent can use, install, learn from, or promote: tools, MCP servers, skills, CLIs, runtimes, remote agents, templates, workflows, automations, examples, and policy metadata.
Why it matters
Agents fail when capability discovery is ad hoc. They either cannot find the right tool, over-expose every tool, or use a capability that is technically available but inappropriate for the task. A registry makes capability selection explicit and governable.
The MCP Registry is the clearest protocol-level example: it stores metadata for public MCP servers, including package/remote execution information and capabilities. But the registry is discovery, not trust. Kevin's stack needs a broader local concept that includes MCP servers, skills, CLIs, browser tools, model/runtime choices, source artifacts, templates, workflow patterns, and approval policy. Source: MCP Registry docs, https://modelcontextprotocol.io/registry/about, 2026-06-18
The registry should not require a capability to be installable. A reusable article, design technique, starter template, eval rubric, browser verification loop, or recurring source-ingest pattern can change agent behavior as much as a package. Those capabilities promote into different surfaces: skill files, wiki pages, trigger evals, automations, source-compile rules, or compact routing docs. Source: User request, 2026-06-25
Registry vs router vs policy
| Layer | Question | Kevin example |
|---|---|---|
| Registry | What capabilities exist, how are they invoked, who owns them, and what do they require? | skills/**/SKILL.md, MCP Registry, Agent Machines web/data/*.json |
| Router | Which capability should this task use first? | Capability Routing Map, Skill Resolver |
| Policy | Is this capability allowed here, with these credentials and side effects? | tool permissions, MCP allowlists, approval gates |
| Action surface | What should an agent run first for a concrete intent? | Actionable Tools Index |
Do not collapse these layers. A registry without routing is a warehouse. A router without a registry is vibes. Policy without either becomes a bureaucratic prompt blob. An action surface without the other three becomes a stale shortcut menu, which is how agents end up confidently reaching for last month's shiny wrench.
Minimum useful schema
| Field | Purpose |
|---|---|
| Name and slug | Stable identity for linking, install, audit, and deprecation |
| Capability class | Tool, skill, CLI, MCP server, remote agent, model, runtime, substrate, preset, template, pattern, automation |
| Source class | Registry, docs, changelog, repo, X bookmark, article, transcript, design folder, product demo |
| Invocation surface | Function schema, CLI command, MCP endpoint, API route, A2A agent card, skill trigger |
| Auth requirements | Tokens, OAuth scopes, local session, BYOK, org credentials |
| Permission tier | Read-only, write, destructive, external spend, private data, production |
| Install/boot instructions | Packages, env vars, setup commands, sandbox requirements |
| Input/output contract | JSON schema, file artifacts, streaming events, token limits |
| Routing hints | Best tasks, anti-tasks, fallback, preferred harness |
| Promotion target | Skill, tool page, design page, workflow, architecture note, automation, trigger eval, source-compile rule |
| Evidence artifacts | Original post, article, repo, demo, screenshot, video, comments, example output |
| Evaluation metadata | Known tests, benchmarks, smoke checks, failure modes |
| Owner and freshness | Maintainer, last verified date, deprecation path |
IRL comparison
| Registry shape | What it gets right | Missing piece |
|---|---|---|
| MCP Registry | Public metadata for MCP servers and install/config discovery | It does not approve trust or quality for Kevin's environment |
| Skills.sh - Agent Skills Registry | Reusable agent procedures distributed as files | Needs local audit, dedupe, and resolver integration |
| Package registries | Versioning and installation at ecosystem scale | Usually unaware of agent safety, task fit, or token cost |
| Agent2Agent (A2A) agent cards | Discovery of remote agent capabilities and modalities | Delegation policy and outcome evaluation still live locally |
| Agent Machines loadout/registry | Product-level bundle of skills, MCPs, service routes, runtimes, and presets | Must keep counts generated and avoid stale marketing constants |
| Source/artifact registries | Finds patterns in posts, comments, docs, demos, transcripts, and design folders | Needs promotion rules so useful artifacts become durable behavior |
State of the art direction
- Public registries standardize metadata.
- Local control planes decide trust, auth, and approval.
- Runtimes expose smaller typed tool surfaces instead of huge undifferentiated lists.
- Skills become installable capabilities, not just prompt snippets.
- Capability metadata starts to include evals, examples, and failure modes.
- Remote agents become discoverable capabilities through A2A-like descriptors, not only tools.
Kevin rule
Before adding a new capability, check whether an existing registry layer already owns it:
- Executable procedure: add or update
skills/**/SKILL.md. - Capability facts and tradeoffs: add or update
wiki/tools/orwiki/concepts/. - Visual/interface technique: add or update
wiki/design/orwiki/style/. - Repeated operational cadence: add or update
automations/and Operational Heartbeat routing. - Source-ingest behavior: add or update Source Compile Workflow or capture rules.
- First-action routing: update Skill Resolver or Capability Routing Map.
- Install/discovery inventory: update the relevant MCP/skill/loadout registry.
- Safety/governance: add permission tier, auth notes, and verification.
If the same tool appears twice, decide whether it is a valid skill/tool mirror before merging.
Harvest layer
Kevin's local capability registry now has a repeatable harvest path: npm run harvest:capabilities snapshots skills.sh, the official MCP Registry, Smithery, the curated CLI seed catalog, and the capability class / non-registry source matrix into raw/registries/agent-capabilities/YYYY-MM-DD/. The snapshots are discovery inventory, not approval. Promotion still happens through Capability Harvest Pattern, npm run promote:capabilities, Skill Resolver, Capability Routing Map, Active Stack (What to Actually Use), trigger evals, and local policy. For SaaS/infra CLIs, Security and Review Skills and Service CLI Coverage are the current horizontal promotion layer. For non-installable patterns, the promotion layer is the natural owning surface: skill, page, automation, test, capture rule, or routing update. Source: User request, 2026-06-22; User request, 2026-06-25
Concept Position
| Field | Value |
|---|---|
| Concept family | Agent harness and runtime primitives |
| Concept owned | An agent capability registry is the catalog of actions, patterns, and source artifacts an agent can use, install, learn from, or promote: t... |
| Category map | Concept System Map |
Timeline
- 2026-07-01 | Concepts category refresh added this page to the Agent harness and runtime primitives family, linked it to Concept System Map, and kept it standalone because it owns this reusable mental model: An agent capability registry is the catalog of actions, patterns, and source artifacts an agent can use, install, learn from, or promote: t... Source: User request, 2026-07-01
- 2026-07-01 | Added Actionable Tools Index as the action-surface layer: registry = what exists, router = what wins, policy = what is allowed, action index = what an agent should run first for a concrete intent. Source: User request, 2026-07-01
- 2026-06-25 | Expanded the registry definition to include non-installable capabilities such as source artifacts, templates, design techniques, eval/review patterns, automations, and source-compile rules. Source: User request, 2026-06-25
- 2026-06-22 | Added a promotion-audit layer and the service CLI registry/coverage pages so harvested SaaS/infra candidates become routed intelligence without blind MCP installation. Source: User request, 2026-06-22
- 2026-06-22 | Added the capability harvest layer: dated raw snapshots for skills.sh, MCP registries, Smithery, and CLI seeds, with promotion kept separate from discovery. Source: User request, 2026-06-22
- 2026-06-18 | Created to explain the shared primitive behind MCP Registry, skills.sh, SKILL-RESOLVER, and Agent Machines loadouts. Source: whole-wiki graph audit, 2026-06-18