Your first rule

--init scaffolds apimock-rule-set.toml, referenced from apimock.toml’s service.rule_sets. Each [[rules]] block is one condition-plus-response pair.

Match on the path alone

[[rules]]
when.request.url_path = ""
respond.text = "home"

[[rules]]
when.request.url_path = "home"
respond.file_path = "home.json"

curl http://localhost:3001/
# --> home
curl http://localhost:3001/home
# --> (content of home.json)

when.request.url_path as a bare string is an exact match. respond.text returns a literal string; respond.file_path serves a file, with its content type inferred from the extension.

Match on method too

[[rules]]
when.request.method = "POST"
when.request.url_path = "/orders"
respond = { text = "order created", status = 201 }

[[rules]]
when.request.method = "GET"
when.request.url_path = "/orders"
respond.text = "order list"

Multiple conditions in one rule are ANDed — both method and url_path have to match. when.request.method is always a bare string: "GET", "POST", "PUT", or "DELETE".

Match on a header

[[rules]]
when.request.url_path = "/private"
[rules.when.request.headers]
authorization = { value = "Bearer eyJhb", op = "starts_with" }
respond.text = "authenticated"

op picks the comparison — starts_with here, equal if omitted. Header names match case-insensitively.

Match on the request body

[[rules]]
when.request.method = "POST"
when.request.url_path = "/orders"
[rules.when.request.body.json]
"customer.tier" = { value = "gold" }
respond.text = "VIP order"

"customer.tier" is apimock’s own dotted-path syntax for reaching into a JSON body — not JSONPath. See Body path syntax before writing anything more complex than one flat key.

What’s next

This is enough to build most mock APIs. Once you outgrow it: Match on URL path and method, Match on headers, and Match on the request body cover every operator available for each; the Guides index covers everything else, including scripting, strategies, TLS, and CI validation.