when data

Each [[rules]] entry contains a when table (e.g., when.request.url_path, when.request.headers, when.request.body.json). This table defines the conditions that an incoming HTTP request must meet for this rule to be triggered.

when.request.url_path

Matches the request's URL path.

# apimock-rule-set.toml
[[rules]]
when.request.url_path = "/greetings"

when.request.headers

Matches specific HTTP headers. You can specify multiple header keys.

• Note: According to RFC 9110, HTTP header field names are case-insensitive. Your mock server will handle this automatically.

# apimock-rule-set.toml
[[rules]]
when.request.headers.user = { value = "user1" }

when.request.body.json

Matches content within the request body. Currently, this supports matching specific keys and values within JSON request bodies.

• JSON Body Matching: You define the target key using dot-notation paths (e.g., request.body.json.order.items.0.product_id). For array fields, use the 0-based index number (e.g., .0).

# apimock-rule-set.toml
[[rules]]
when.request.body.json.order.items.0.product_id = { value = "123" }

Multiple conditions strategy

Important: If you define multiple conditions (e.g., a path, a header, and a body match) within a single [[rules]] block, they are all evaluated using AND logic. All conditions must be met for the rule to match the incoming request.