> ## Documentation Index > Fetch the complete documentation index at: https://docs.revilico.bio/llms.txt > Use this file to discover all available pages before exploring further. # Start a RevSaddle run > Double-ended transition-state search: grows a string from reactant to product, refines its highest points to a first-order saddle and checks the saddle connects the two. Starts a run and returns it with status `queued`; poll GET /v1/runs/{runId} until it finishes. Runs spend credits. **Limits:** `maxAtoms`: 200, `maxGuesses`: 10. **Scope:** `runs:write`. ## OpenAPI ````yaml /api-reference/openapi.json post /v1/engines/revsaddle/runs openapi: 3.1.0 info: title: Revilico API version: 1.0.0 description: >- Run Revilico's computational chemistry and biology engines from your own code: upload input files, start runs, follow them and read their results. servers: - url: https://public-api.revilico.bio security: - bearerAuth: [] tags: - name: Account description: Who you are, your credits and what your runs have used. - name: Engines description: The engines you can run, their parameter schemas and examples. - name: Files description: 'Upload input files: create an upload, then PUT the bytes.' - name: Runs description: Start, follow and cancel engine runs. - name: Results and outputs description: 'Read what a run produced: results, files and outputs.' - name: Projects description: Group runs into the projects you see in the web app. - name: Engine runs description: >- Start a run of one engine, with that engine's parameters and input files. Same endpoint as **Start a run**. - name: Health description: Service status. Needs no API key. paths: /v1/engines/revsaddle/runs: post: tags: - Engine runs summary: Start a RevSaddle run description: >- Double-ended transition-state search: grows a string from reactant to product, refines its highest points to a first-order saddle and checks the saddle connects the two. Starts a run and returns it with status `queued`; poll GET /v1/runs/{runId} until it finishes. Runs spend credits. **Limits:** `maxAtoms`: 200, `maxGuesses`: 10. **Scope:** `runs:write`. operationId: engineRuns.revsaddle requestBody: required: true content: application/json: schema: type: object properties: name: description: A name for the run, shown in the web app. type: string maxLength: 200 parameters: type: object properties: charge: default: 0 type: integer minimum: -10 maximum: 10 multiplicity: default: 1 type: integer minimum: 1 maximum: 11 optimize_inputs: default: true description: Optimise the reactant and product to minima first. type: boolean optimize_ts: default: true description: >- Refine each transition-state guess to a first-order saddle. type: boolean max_guesses: default: 3 description: >- Most transition-state guesses taken from the string and refined. type: integer minimum: 1 maximum: 10 search: default: {} type: object properties: method: default: fsm description: >- fsm (freezing string: each node relaxed briefly then frozen; cheapest) or gsm (growing string: every node keeps relaxing; closer to the minimum-energy path, several times the cost). type: string enum: - fsm - gsm interpolation: default: geodesic description: >- How the string is drawn between reactant and product: geodesic (the best default), lst (try when the geodesic saddle is not the reaction’s) or cartesian (small or rigid changes). type: string enum: - geodesic - lst - cartesian step_size_angstrom: default: 0.3 description: Spacing between string nodes, in Å. type: number minimum: 0.05 maximum: 2 node_steps: default: 2 description: Optimisation steps per node as the string grows. type: integer minimum: 0 maximum: 20 additionalProperties: false verify: default: {} type: object properties: enabled: default: true description: >- Follow an IRC down from the saddle to check it connects the reactant to the product. type: boolean additionalProperties: false settings: default: {} type: object properties: backend: default: aimnet2 description: >- aimnet2 (fast neural network, closed-shell organics only), gfn2-xtb / gfn1-xtb (semiempirical, H-Rn, open-shell), or dft (GPU, most accurate, slowest). type: string enum: - aimnet2 - gfn2-xtb - gfn1-xtb - dft model: default: null description: >- DFT functional (dft backend only); null picks r2scan-d4. anyOf: - type: string enum: - r2scan-d4 - wb97m-d3bj - type: 'null' basis: default: def2-svp description: >- DFT basis set; must stay def2-svp for the other backends. type: string enum: - def2-svp - pcseg-1 - def2-tzvp precision: default: float32 type: string enum: - float32 - float64 optimizer_mode: default: standard type: string enum: - draft - standard - fine - ultrafine - exhaustive max_optimizer_steps: default: 250 type: integer minimum: 1 maximum: 2000 max_scf_iterations: default: 500 description: SCF iteration cap per gradient (dft backend). type: integer minimum: 1 maximum: 2000 additionalProperties: false additionalProperties: false inputs: type: object properties: reactant: type: string description: >- The reactant, one structure with 3D coordinates: XYZ, SDF, MOL or MOL2 (up to 200 atoms). Give it with product, or use structures instead. A file id (`file_…`). Formats: xyz, sdf, mol, mol2; up to 10 MB. product: type: string description: >- The product, one structure with the same atoms in the same order as the reactant. A file id (`file_…`). Formats: xyz, sdf, mol, mol2; up to 10 MB. structures: type: string description: >- Reactant and product in one file, exactly two structures, reactant first. Use instead of reactant + product. A file id (`file_…`). Formats: xyz, sdf, mol, mol2; up to 10 MB. ts_guess: type: string description: >- Optional transition-state guess, one structure with the same atoms in the same order as the reactant. A file id (`file_…`). Formats: xyz, sdf, mol, mol2; up to 10 MB. additionalProperties: false budget: description: Most credits the run may spend; it is stopped beyond that. type: number exclusiveMinimum: 0 projectId: description: >- Add the run to this project (`proj_…`); needs editor or owner on it. type: string additionalProperties: false examples: reactant-and-product: summary: >- Find the transition state between a reactant and a product with AIMNet2 on the defaults (freezing string, geodesic, verified). value: name: Claisen rearrangement TS parameters: {} inputs: reactant: file_… product: file_… one-file-growing-string: summary: >- Reactant and product in one multi-structure file (reactant first), growing string with GFN2-xTB. value: parameters: max_guesses: 5 search: method: gsm interpolation: lst settings: backend: gfn2-xtb inputs: structures: file_… dft-with-guess: summary: >- DFT (r2SCAN-D4/def2-SVP) refinement starting from your own transition-state guess. value: parameters: settings: backend: dft model: r2scan-d4 inputs: reactant: file_… product: file_… ts_guess: file_… responses: '202': description: OK content: application/json: schema: $ref: '#/components/schemas/Run' '400': $ref: '#/components/responses/400' '401': $ref: '#/components/responses/401' '402': $ref: '#/components/responses/402' '403': $ref: '#/components/responses/403' '404': $ref: '#/components/responses/404' '422': $ref: '#/components/responses/422' '500': $ref: '#/components/responses/500' '502': $ref: '#/components/responses/502' components: schemas: Run: type: object properties: id: type: string description: Run id, `run_…`. engine: type: string description: Engine slug, e.g. `revredox`. name: type: - string - 'null' status: type: string enum: - queued - running - succeeded - failed - cancelled description: >- queued until the engine picks the run up; succeeded, failed and cancelled are final. statusReason: description: >- Why a cancelled run stopped: `user`, `insufficient_credits` or `budget_exceeded`. Null otherwise. type: - string - 'null' progress: type: number description: Progress the engine reports; 0 until it reports any. createdAt: type: string format: date-time startedAt: anyOf: - type: string format: date-time - type: 'null' endedAt: anyOf: - type: string format: date-time - type: 'null' budget: description: Most credits the run may spend, if one was set. type: - number - 'null' creditsUsed: type: number description: Credits charged to the run so far. error: anyOf: - type: object properties: message: type: string required: - message - type: 'null' description: Set when status is failed. links: type: object propertyNames: type: string additionalProperties: type: string description: 'Related endpoints: self, inputs, results, outputs, files.' warnings: description: >- Set when the run was created but a follow-up step, such as adding it to a project, failed. type: array items: type: string required: - id - engine - name - status - statusReason - progress - createdAt - startedAt - endedAt - budget - creditsUsed - error - links Error: type: object properties: error: type: object properties: code: type: string enum: - VALIDATION_FAILED - INVALID_ID - INVALID_PARAMETERS - INPUT_LIMIT_EXCEEDED - NOT_FOUND - FORBIDDEN - METHOD_NOT_ALLOWED - CONFLICT - PAYLOAD_TOO_LARGE - MISSING_CREDENTIALS - INVALID_CREDENTIALS - WRONG_ENVIRONMENT - CREDENTIALS_EXPIRED - CREDENTIALS_REVOKED - ACCOUNT_INACTIVE - API_ACCESS_NOT_ENABLED - INSUFFICIENT_SCOPE - SESSION_REQUIRED - TOO_MANY_AUTH_FAILURES - API_KEY_LIMIT_REACHED - ENGINE_NOT_ENABLED - DOCS_NOT_AVAILABLE - INSUFFICIENT_CREDITS - RUN_NOT_COMPLETE - ENGINE_SUBMIT_FAILED - RATE_LIMITED - SERVICE_UNAVAILABLE - INTERNAL_ERROR description: Stable within /v1; branch on this, not on the message. message: type: string description: Readable explanation, for people. details: description: >- Extra context, e.g. `issues` ({ path, message }[]) for validation errors. type: object propertyNames: type: string additionalProperties: {} required: - code - message required: - error responses: '400': description: >- The request is malformed. `error.code` is one of `VALIDATION_FAILED`, `INVALID_ID`. content: application/json: schema: $ref: '#/components/schemas/Error' example: error: code: VALIDATION_FAILED message: The request is malformed. '401': description: >- The API key is missing or not valid. `error.code` is one of `MISSING_CREDENTIALS`, `INVALID_CREDENTIALS`, `WRONG_ENVIRONMENT`, `CREDENTIALS_EXPIRED`, `CREDENTIALS_REVOKED`. content: application/json: schema: $ref: '#/components/schemas/Error' example: error: code: MISSING_CREDENTIALS message: The API key is missing or not valid. '402': description: >- Your organization doesn't have enough credits. `error.code` is one of `INSUFFICIENT_CREDITS`. content: application/json: schema: $ref: '#/components/schemas/Error' example: error: code: INSUFFICIENT_CREDITS message: Your organization doesn't have enough credits. '403': description: >- The key may not do this. `error.code` is one of `INSUFFICIENT_SCOPE`, `API_ACCESS_NOT_ENABLED`, `ENGINE_NOT_ENABLED`, `ACCOUNT_INACTIVE`, `FORBIDDEN`. content: application/json: schema: $ref: '#/components/schemas/Error' example: error: code: INSUFFICIENT_SCOPE message: The key may not do this. '404': description: Not found, or not visible to you. `error.code` is one of `NOT_FOUND`. content: application/json: schema: $ref: '#/components/schemas/Error' example: error: code: NOT_FOUND message: Not found, or not visible to you. '422': description: >- The parameters or input files don't fit the engine. `error.code` is one of `INVALID_PARAMETERS`, `INPUT_LIMIT_EXCEEDED`. content: application/json: schema: $ref: '#/components/schemas/Error' example: error: code: INVALID_PARAMETERS message: The parameters or input files don't fit the engine. '500': description: >- Something went wrong on our side. `error.code` is one of `INTERNAL_ERROR`. content: application/json: schema: $ref: '#/components/schemas/Error' example: error: code: INTERNAL_ERROR message: Something went wrong on our side. '502': description: >- The engine service rejected or failed the request. `error.code` is one of `ENGINE_SUBMIT_FAILED`. content: application/json: schema: $ref: '#/components/schemas/Error' example: error: code: ENGINE_SUBMIT_FAILED message: The engine service rejected or failed the request. securitySchemes: bearerAuth: type: http scheme: bearer description: >- An API key from the web app (**Settings → Developer**), sent as `Authorization: Bearer rvl_live_…`. ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.