Agent Skill · Anthropic
MCP builder skill
Anthropic's published skill for building MCP servers — scaffolding, protocol conventions and tool design guidance for new connectors.
This skill bundles executable code. Scripts shipped alongside the instructions run with the permissions of the engineer running the agent. Review the scripts, not only the SKILL.md.
What it is, and what it costs you
This skill teaches an agent to build MCP servers: the protocol's shape, how to define tools and their schemas, how to structure a server that behaves correctly against a client. It is a good example of a skill whose value is compressed expertise — the protocol has conventions that are obvious once known and expensive to rediscover.
Its governance interest is second-order and specific. This skill produces artifacts that themselves become part of the AI supply chain. An MCP server written by an agent following this skill will be connected to other agents, granted credentials, and given a place in the trust boundary. Whatever the skill teaches about tool design, error handling, and authorization propagates into every server built with it.
That makes tool-description quality a security property rather than a documentation nicety. Descriptions are read by models as instruction, so a generated server with vague or over-broad descriptions produces agents that call tools in situations their author never intended. Likewise, a server scaffolded with a single broad credential rather than per-request identity propagation bakes in the confused-deputy pattern at birth.
The reasonable expectation for any team adopting this is that generated servers enter the same review path as hand-written ones. An agent-authored connector is not pre-approved by virtue of having been generated from a reputable skill.
Capability profile
What this skill can reach inside your environment, and why a security team cares. Derived from the publisher's documentation, not from a scan.
- bundled script execution
Scaffolding and validation code runs with the invoking user's permissions.
- code generation into the AI supply chain
Produces connectors that will later hold credentials and sit inside the agent trust boundary.
- filesystem write
Creates project structure and source files in the working directory.
Before you distribute this to a team
- Review generated servers like any other connector
Being agent-authored from a reputable skill is not an approval. Check credential scope, tool descriptions and authorization handling.
- Require per-request identity, not a shared credential
A scaffolded server with one broad token embeds the confused-deputy problem. Fix it at generation time, not after deployment.
- Treat tool descriptions as a security artifact
Descriptions are instructions to a model. Narrow, precise descriptions are a control; vague ones are a liability.
Vincosha Assay assessment
not yet assessedWe have not published a scan verdict for MCP builder skill.
Everything above is a capability profile compiled by hand from the publisher's own public documentation on 2026-07-25. It describes what this artifact can reach and what to restrict before rolling it out. It is not a security verdict, and it should not be read as one.
When Vincosha Assaypublishes an assessment for this artifact it will appear here with a verdict, the findings behind it, and the date it ran. We would rather leave this space empty than fill it with a guess — inventing a security verdict about somebody else's software would be both wrong and dangerous.
What an assessment covers
- prompt-injection patterns in descriptions and instructions
- credential reads and outbound egress in bundled code
- over-scoped permissions and manifest claims
- typosquatted and impersonating names
- tool-manifest drift since the last approval
- content hash against the version you approved
Sources
Compiled from the publisher's own documentation and repository. Skills change — read the version you are about to install rather than trusting a profile.