HTTP Assertions

Assertions define what “healthy” means for your HTTP monitor. Each check evaluates all assertions and records a pass or fail result. A failed fail-severity assertion causes the check to fail; a failed warn-severity assertion records a DEGRADED hint without triggering a DOWN incident.

Severity levels

Severity	Behavior
`fail`	Check is marked as failed. Contributes to incident trigger rules.
`warn`	Check passes but records a `DEGRADED` severity hint. Can trigger `degraded` incident rules.

Assertion types

status_code

Validate the HTTP response status code.

Field	Type	Required	Description
`expected`	string	Yes	Expected status code (e.g., `"200"`, `"2xx"`)
`operator`	string	Yes	`equals`, `contains`, `matches`, `range`

assertions:
  - config:
      type: status_code
      expected: "200"
      operator: equals
    severity: fail

Use range to match a range of status codes:

assertions:
  - config:
      type: status_code
      expected: "200-299"
      operator: range
    severity: fail

response_time

Fail when response latency exceeds a threshold.

Field	Type	Required	Description
`thresholdMs`	integer	Yes	Maximum acceptable response time in milliseconds

assertions:
  - config:
      type: response_time
      thresholdMs: 2000
    severity: fail

response_time_warn

Record a degraded hint when response time is elevated but not critical.

Field	Type	Required	Description
`warnMs`	integer	Yes	Warning threshold in milliseconds

assertions:
  - config:
      type: response_time_warn
      warnMs: 1000
    severity: warn

Use response_time with fail severity for outage detection and response_time_warn with warn severity for early degradation alerts.

body_contains

Check that the response body contains a specific substring.

Field	Type	Required	Description
`substring`	string	Yes	Text to search for in the response body

assertions:
  - config:
      type: body_contains
      substring: '"status":"ok"'
    severity: fail

json_path

Extract a value from a JSON response using JSONPath and compare it.

Field	Type	Required	Description
`path`	string	Yes	JSONPath expression (e.g., `$.status`)
`expected`	string	Yes	Expected value
`operator`	string	Yes	`equals`, `contains`, `less_than`, `greater_than`, `matches`, `range`

assertions:
  - config:
      type: json_path
      path: $.status
      expected: healthy
      operator: equals
    severity: fail

header_value

Validate a response header value.

Field	Type	Required	Description
`headerName`	string	Yes	Response header name
`expected`	string	Yes	Expected value
`operator`	string	Yes	`equals`, `contains`, `less_than`, `greater_than`, `matches`, `range`

assertions:
  - config:
      type: header_value
      headerName: content-type
      expected: application/json
      operator: contains
    severity: fail

regex_body

Match the response body against a regular expression.

Field	Type	Required	Description
`pattern`	string	Yes	Regular expression pattern

assertions:
  - config:
      type: regex_body
      pattern: '"version":\s*"\d+\.\d+\.\d+"'
    severity: fail

ssl_expiry

Alert before TLS certificates expire. Requires verifyTls: true (the default).

Field	Type	Required	Description
`minDaysRemaining`	integer	Yes	Minimum days until expiry

assertions:
  - config:
      type: ssl_expiry
      minDaysRemaining: 30
    severity: warn
  - config:
      type: ssl_expiry
      minDaysRemaining: 7
    severity: fail

Stack two ssl_expiry assertions: warn at 30 days for early notice, fail at 7 days for urgent action. See the SSL certificate monitoring guide.

response_size

Limit the response body size.

Field	Type	Required	Description
`maxBytes`	integer	Yes	Maximum response size in bytes

assertions:
  - config:
      type: response_size
      maxBytes: 1048576
    severity: warn

redirect_count

Limit the number of redirects followed.

Field	Type	Required	Description
`maxCount`	integer	Yes	Maximum number of redirects

assertions:
  - config:
      type: redirect_count
      maxCount: 3
    severity: warn

redirect_target

Verify the final redirect destination URL.

Field	Type	Required	Description
`expected`	string	Yes	Expected final URL
`operator`	string	Yes	`equals`, `contains`, `matches`

assertions:
  - config:
      type: redirect_target
      expected: https://www.example.com
      operator: equals
    severity: fail

Operators reference

Operator	Behavior	Applies to
`equals`	Exact string or numeric match	`status_code`, `json_path`, `header_value`, `redirect_target`
`contains`	Substring match	`status_code`, `json_path`, `header_value`, `redirect_target`
`less_than`	Numeric less-than	`json_path`, `header_value`
`greater_than`	Numeric greater-than	`json_path`, `header_value`
`matches`	Regex match	`status_code`, `json_path`, `header_value`, `redirect_target`
`range`	Numeric range (e.g., `"200-299"`)	`status_code`, `json_path`, `header_value`

Common patterns

Health check with status + latency

assertions:
  - config:
      type: status_code
      expected: "200"
      operator: equals
    severity: fail
  - config:
      type: response_time
      thresholdMs: 3000
    severity: fail
  - config:
      type: response_time_warn
      warnMs: 1500
    severity: warn

JSON API validation

assertions:
  - config:
      type: status_code
      expected: "200"
      operator: equals
    severity: fail
  - config:
      type: json_path
      path: $.status
      expected: healthy
      operator: equals
    severity: fail
  - config:
      type: header_value
      headerName: content-type
      expected: application/json
      operator: contains
    severity: fail

SSL + uptime combo

assertions:
  - config:
      type: status_code
      expected: "200"
      operator: equals
    severity: fail
  - config:
      type: ssl_expiry
      minDaysRemaining: 30
    severity: warn
  - config:
      type: ssl_expiry
      minDaysRemaining: 7
    severity: fail

Next steps

HTTP configuration

Headers, body, TLS, and auth fields.

SSL monitoring guide

Certificate expiry monitoring patterns.

Incident policies

How assertion failures trigger incidents.

Monitoring as Code

Define assertions in YAML.

Getting Started

Monitoring as Code

Monitoring

Incidents

Alerting

Status Data

Platform

Common Patterns

HTTP Assertions

Severity levels

Assertion types

status_code

response_time

response_time_warn

body_contains

json_path

header_value

regex_body

ssl_expiry

response_size

redirect_count

redirect_target

Operators reference

Common patterns

Next steps

HTTP configuration

SSL monitoring guide

Incident policies

Monitoring as Code

​Severity levels

​Assertion types

​status_code

​response_time

​response_time_warn

​body_contains

​json_path

​header_value

​regex_body

​ssl_expiry

​response_size

​redirect_count

​redirect_target

​Operators reference

​Common patterns

​Next steps

HTTP configuration

SSL monitoring guide

Incident policies

Monitoring as Code

Severity levels

Assertion types

status_code

response_time

response_time_warn

body_contains

json_path

header_value

regex_body

ssl_expiry

response_size

redirect_count

redirect_target

Operators reference

Common patterns

Next steps