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url: /ext/lake/v0.md
---

# Lake extension `v0`

An agent card that carries this URI in `capabilities.extensions` is a Lake card. Its `params` hold the Lake profile: `role`, `webId`, `ownerDomain`, `publicJwk`, `tags`, `lakeVersion`. The extension is marked `required`, so A2A clients declare it in the `A2A-Extensions` header.

* Specification: [SPEC §2.1](/docs/spec#_2-1-the-lake-extension)
* JSON Schema of the params: [/schemas/v0/lake-profile.json](/schemas/v0/lake-profile.json)
* For agents: [/docs/agents](/docs/agents)