diff --git a/docs/mcp.md b/docs/mcp.md
index 66459255a..b12a00365 100644
--- a/docs/mcp.md
+++ b/docs/mcp.md
@@ -1387,9 +1387,13 @@ vectorcraft-cli run --cmd file.new --params '{"width":600,"height":200}'   --cmd
 Some commands have a machine-readable parameter schema: at present `view.capsLock`, `view.saved.new`,
 `view.saved.edit`, `view.saved.list`, `view.transparencyGrid` and `view.snapToGlyph.options`. The engine's
 `engine.commands` list gives such a command a `schema` field: an object schema in the shape of JSON Schema 2020-12
-(https://json-schema.org/draft/2020-12), with `type`, `properties`, `required`, `additionalProperties: false`,
-`minimum`, `maximum`, `exclusiveMinimum` and `exclusiveMaximum` for ranges, `enum`, and `default` for a default the engine fills in. VectorCraft's own
-fields are `x-since` (the API level that added the command or the parameter), `x-deprecatedSince`, `x-lenient`,
+(https://json-schema.org/draft/2020-12). Its root has `$schema` (the 2020-12 dialect), `description` when the
+command has a summary, and `deprecated: true` when the command is deprecated. The schema uses `type`, `properties`, `required` and
+`additionalProperties: false` for objects; `minimum`, `maximum`, `exclusiveMinimum` and `exclusiveMaximum` for ranges;
+`enum` for a list of names; `items` for the values of a list; `prefixItems`, `items: false` and `minItems: 2` for a
+point; `anyOf` and `minItems: 3` for a color, which is a string, a list of at least three numbers or an object;
+`description` for a parameter's doc text; `default` for a default the engine fills in; and `deprecated: true` for a
+deprecated parameter. VectorCraft's own fields are `x-since` (the API level that added the command or the parameter), `x-deprecatedSince`, `x-lenient`,
 `x-unit`, `x-kind` (`id`, `color` or `point`), `x-default` (a default the command works out, such as `toggle`),
 `x-cost`, `x-writes` (`nothing`, `session`, `preferences` or `document`) and `x-returns`. A parameter that reads null
 as left out is an `anyOf` with `{"type": "null"}`. Null params read as `{}`, so a schema with no required parameter has