APIs.io indexes 1,535 Agent Skills published by 114 providers. It is the newest artifact type on the network and the fastest-moving one.
An Agent Skill is a small, named unit of instruction that tells an agent when to do something and how — narrower than a specification, more opinionated than documentation, and written for a consumer that has no prior knowledge of your product.
What one actually looks like
Take ActiveCampaign, which publishes 6 skills covering Postmark:
| Skill | Purpose |
|---|---|
postmark |
Router — dispatches to the right sub-skill |
postmark-send-email |
Single, batch (up to 500), bulk, template-based sends |
postmark-inbound |
Reply-by-email, email-to-ticket, document extraction |
postmark-templates |
Handlebars templates, layout inheritance, cross-server pushing |
postmark-webhooks |
Delivery, bounce, open, click, spam and subscription tracking |
postmark-email-best-practices |
Deliverability, CAN-SPAM, GDPR, CASL — provider-agnostic |
Read the descriptions and a pattern emerges. Every one begins with “Use when…”.
That is the whole design. A specification describes what exists. A skill describes the conditions under which you should reach for it. The router skill — a skill whose only job is dispatching to other skills — is the tell that these are being written as a system rather than as documentation with a new file extension.
The best one is not about the product
postmark-email-best-practices covers deliverability, compliance and testing safely, and is explicitly marked provider-agnostic.
A vendor shipping an agent-facing skill that does not sell the vendor is a genuinely interesting move. It says: before you use our sending API, here is how not to get your domain blocked, whichever provider you end up on. That is the sort of thing that used to live in a blog post nobody read at the right moment. Attached as a skill, it arrives exactly when an agent is about to send its first bulk email.
114 providers is small and the shape is right
Against 26,530 providers in the catalog, 114 is under half a percent. The category is months old.
What matters more than the count is what the early adopters look like. The 114 skew toward developer tooling and infrastructure — ActiveCampaign, Airtable, Amazon SES, Amplitude, Apify, APIMATIC, Apollo GraphQL, Appwrite, AssemblyAI, Atlassian, Autodesk, Azure, Canva, Cerbos, Checkly. These are companies whose customers were always going to wire them into something.
That is the same adoption curve OpenAPI ran in 2012 and MCP ran last year: infrastructure vendors first, because their buyers demand machine-readable everything, and the rest of the catalog eighteen months later.
Skills versus MCP servers
These are complementary and frequently confused. An MCP server is a transport — it exposes tools an agent can call. A skill is guidance — it tells the agent which tool, when, and what to watch out for.
Auth0, covered earlier this week, publishes both. Almost nobody else does.
Takeaway
1,535 skills from 114 providers, dominated by infrastructure vendors, structured around “Use when…” and occasionally generous enough to include advice that does not sell anything. It is early — under half a percent of the catalog — and the shape of what is being published is more encouraging than the count.
Browse the network at apis.io.