---
title: "Design a non-repetitive promoter library spanning a strength range"
method: POST
path: "/promoter_library_design"
tags: ["Analysis"]
---

# Design a non-repetitive promoter library spanning a strength range

`POST /promoter_library_design`

## Request

- Base URL: `https://seqbench.com/api/v1`
- URL: `https://seqbench.com/api/v1/promoter_library_design`
- Auth: none required

Build a set of sigma-70 promoters that (a) share no more than a chosen length of sequence with each other, so the library does not recombine with itself once integrated, and (b) span a range of predicted transcription rates, picked as an evenly log-spaced ladder. Variants are constructed deterministically from an IUPAC template holding the -35 and -10 consensus; their strengths are then estimated by the Promoter Calculator model. Rungs with no variant near them are reported as gaps rather than filled with the nearest thing. PREDICTED, NOT MEASURED: strengths carry R^2 = 0.45-0.60 against independent in vivo data, so treat the ladder as a ranked set to screen, not as calibrated numbers.

## Request body

- object
  - `librarySize` integer, required: How many promoters the ladder should have (2 to 24). Required: every other argument has a defensible default, so this is the one statement of intent, and without it an empty call would build and score a library nobody asked for.
  - `targetMin` number: Weakest rung, in the model's arbitrary transcription-rate units. OMIT THIS and the range is taken from what the built variants actually score, which is usually right: the units have no absolute meaning, so a default would describe nothing. Set it only to match a promoter you measured yourself.
  - `targetMax` number: Strongest rung, same units. Omit with targetMin to use the variants' own range.
  - `lmax` integer: Longest stretch any two promoters in the library may share, in bp (default 12). This is the property that stops the library recombining with itself.
  - `template` string: IUPAC template every variant must match. Defaults to a sigma-70 layout holding TTGACA and TATAAT with a 17 nt spacer and randomised flanks. Change it to target a different architecture — but a template that randomises the boxes will produce members that are not promoters.
  - `candidatePool` integer: How many variants to build and score before selecting the ladder. A larger pool fills more rungs and costs one longer scan, not more round trips.
  - `gcMin` number: Lowest GC% a variant may have.
  - `gcMax` number: Highest GC% a variant may have.
  - `exclude` string[]: Motifs no variant may contain, both strands — the restriction sites you clone with. Literal ACGT only.
  - `seed` integer: Seeds variant construction; same seed, same variants.

## Response `200`

Tool ran successfully.

- SuccessResponse: Standard success envelope returned by every single-tool call.
  - `ok` unknown, required
  - `tool` string, required: The tool slug that ran.
  - `result` object, required: Tool-specific output object. Its shape depends on the tool — call `GET /{tool}` or see the docs for each tool's fields.
  - `gate` GateResult
    - `pass` boolean, required: True if and only if every hard check passed.
    - `checks` GateCheck[], required
      - `id` string, required
      - `label` string, required
      - `severity` 'hard' | 'soft', required
      - `pass` boolean, required
      - `message` string, required
      - `value` number
      - `threshold` string
    - `notChecked` string[], required: Honest list of what this gate does NOT verify.
  - `provenance` Provenance, required
    - `apiVersion` string, required
    - `tool` union, required: Tool slug, or an array of slugs (one per step) for a workflow.
      - string
      - string[]
    - `generatedAt` string, date-time, required: ISO 8601 timestamp of when the result was generated.

## Other responses

- `400`: Invalid argument or the tool could not run.
- `404`: Unknown tool.
- `429`: Rate limited (metered tools only). Body carries code `rate_limited` and retryable `true`; honor the Retry-After header.
- `503`: A metered tool is momentarily at capacity. The identical request should succeed after Retry-After; body carries code `upstream_unavailable`.

---

[API](https://skmtc.dev/seqbench/apis/seqbench-api.md) · [All operations](https://skmtc.dev/seqbench/apis/seqbench-api/llms.txt) · [OpenAPI document](https://skmtc.dev/seqbench/apis/seqbench-api/revisions/132575216865?raw)