Create a routine.

Creates a routine with a single webhook trigger in the given projectId. POSTing JSON to the returned webhookUrl runs the routine's prompt in a new workspace as the routine owner, using the owner's credentials for the selected agent. The webhookUrl is the trigger's only credential and is returned here and from rotate-secret only; treat it as a secret. Requires a user API key: workspace API keys and other sign-in credentials receive 403. The routine is owned by the key's user in the key's organization. Accepted model ids by agent — claude: fable-5-1, fable-5, opus-5-5-1m, opus-5-1m, opus-4-8-1m, opus-4-8, opus-4-7-1m, opus-4-7, opus-4-6-1m, sonnet-5-5-1m, sonnet-5-1m, sonnet-4-6-1m, sonnet-4-6, haiku-5-5-1m, haiku-4-5; codex: gpt-5.5, gpt-5.4, gpt-5.6-sol, gpt-5.6-terra, gpt-5.6-luna, gpt-5.3-codex-spark, gpt-5.3-codex, gpt-5.2-codex, gpt-6-astra, gpt-6.1-sol, gpt-6-sol, gpt-6-luna, gpt-daybreak-blue-latest; cursor: auto, composer-2.5, grok-4.7, grok-4.6, grok-4.5. Accepted effort levels by agent — claude: low, medium, high, xhigh, max, ultracode; codex: none, low, medium, high, xhigh, max, ultra; cursor: low, medium, high, xhigh; codex max and ultra, and claude ultracode, require support from the selected model. Omit effort to use the agent's default — claude: high; codex: high.