> For a complete index of all SignalWire documentation pages, fetch https://signalwire.com/docs/llms.txt # Errors > Error codes emitted by SWML during script execution, for both calling and messaging documents. Reference for the error codes that SWML reports when a document fails to fetch, parse, or run. Calling and messaging SWML use different code namespaces: * **Calling errors** start with `relay_script_*` and surface on the call session as the `script_error` variable and as `calling.script.warning` events. * **Messaging errors** include the `swml_*` codes for messaging-specific failures plus a handful of document-level codes. They appear on the inbound message in the [Messaging logs](/docs/apis/rest/message-logs/list-message-logs) and on any status callbacks you've configured. ## Calling errors Errors raised while executing a calling SWML document. Each error is reported with a contextual message describing the offending method, parameter, or condition. You can read the code from the `script_error` variable on the call session or from the payload of the `calling.script.warning` event. The fetched document could not be parsed as valid JSON or YAML, or the `dest` URL of a `transfer` was malformed. An internal parsing error occurred while reading the document. Verify the document is valid YAML or JSON and retry. The document's `version` value is not a supported SWML version. The document has no `sections` element. The document's `sections` is missing the required `main` section. A section is defined but contains no executable steps. An `execute` step references a section that does not exist in the document. An unrecognized top-level element appears in the document. A document element has the wrong JSON type for its position (for example, an array where an object was expected). A document element has an invalid value (for example, an enum-valued field set to an unrecognized string). A document element that may appear at most once was provided multiple times. A step in a section does not have a method name (the step entry is malformed). A step references a method that is not a recognized SWML calling method. A required parameter for the method is missing — for example, `transfer` without `dest`, or `request` without `url`. A method parameter has an invalid value — for example, a `request.method` that is not one of the supported HTTP verbs, or a `switch.variable` that does not resolve to a valid variable name. A method received a parameter name it does not recognize. Two mutually-exclusive parameters were provided on the same method. A `switch` step matched no `case` and no `default` was provided. A method failed while running — for example, a media playback failure, a transfer that couldn't dial, or a tap or stream that couldn't be set up. The accompanying message provides the specific cause. A JavaScript expression in a `cond`, `switch`, `eval`, or `when` clause raised an error. A document or one of its sections is nested beyond the maximum depth. The chain of `transfer` and `goto` steps exceeded the platform maximum (32 transfers per call). An internal server error occurred during script execution. ## Messaging errors Errors emitted when an inbound message's SWML document fails to fetch, parse, or execute. Each inbound message is marked `failed` with the listed `error_code` and a corresponding `error_message`, visible in the [Messaging logs](/docs/apis/rest/message-logs/list-message-logs). ### Document fetch / route Unrouteable message received — no SWML handler is assigned to the inbound number. Insufficient account balance to receive the message. Message filtered (e.g. spam detection or carrier-level filtering). The attempt to retrieve the SWML document timed out or failed. The configured SWML URL could not be parsed. ### Document parse The document must be valid JSON or YAML. Document may contain only one of `reply`, `receive`, or `sections` at the top level. Document must contain `reply`, `receive`, or `sections`. Section `main` must be an array of steps. The document references an unsupported SWML messaging method. ### `reply` method Failed to create the reply message (general fallback for reply persistence errors). The reply exceeds the maximum of 8 media attachments. The reply must include a `body` or `media`. The reply `from` number is not a valid PhoneRoute or ShortCode in this project. The reply `to` number has an invalid format. The reply `from` number is not SMS- or MMS-capable for the kind of message being sent. The reply body exceeds the character limit for the destination. The reply `from` number must belong to an active 10DLC campaign. ### `switch` method `switch` matched no `case` and no `default` was provided. `switch.transform` is not one of `lowercase`, `uppercase`, `trim`, `lowercase_trim`, `uppercase_trim`. ### `execute` method The section named by `execute.dest` is not defined in the current document. ### `transfer` method `transfer.dest` is required and was missing or empty. Failed to fetch the transferred SWML document from the destination URL. The transferred SWML document is not a valid messaging document. ### `goto` method `goto.label` does not match any `label` step in the current section. ### `request` method `request.url` is required and was missing or empty.