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CRISPR Off-Target Similarity Scorer
x402
CRISPR Off-Target Similarity Scorer is a paid API for AI agents from bio.halowerk.com, paid per call via x402, $0.004/call, status unknown (last checked 2026-09-14).
Ranks user-supplied candidate protospacers against a guide RNA sequence using a mismatch-weighted similarity score with NGG PAM penalty, emphasizing the guide's seed region (final 10 positions).
Price / call$0.004
Success—
StatusUnknown
How this service works
Compares one guide with caller-supplied candidate protospacers, weights mismatches in the guide’s final ten positions twice, applies a simple NGG PAM penalty, and ranks a transparent similarity score. It does not search a genome, model bulges, chromatin or nuclease-specific biology, and must not be used as a clinical or laboratory safety decision.
Output
Returns a ranked list of candidate protospacers with a transparency similarity score for each, factoring in double-weighted mismatches in the guide's final 10 positions (seed region) and an NGG PAM penalty. Does not perform genome search, model bulges, chromatin accessibility, or nuclease-specific biology.
Example use cases
Screen candidate off-target sites pre-experiment
“I have a 20-nt CRISPR guide sequence GTATCGATCGATCGATCGAT and a list of 50 genomic candidates with their protospacers and NGG PAMs — can you score and rank them by off-target similarity so I know which ones to worry about before I run my experiment?”
Validate guide specificity for research paper
“For my manuscript I need to show my guide RNA ACGATCGATCGATCGATCGA has low off-target risk — please score these 10 candidate sequences with their PAMs against it and give me a ranked similarity table I can include.”
Triage off-target candidates from alignment hits
“I pulled 200 candidate protospacer hits from a BLAST search against my guide TTGCAACGTACGTTGCAACG, each with an ID and PAM — can you run them through the seed-region mismatch scorer and tell me which top 10 have the highest similarity scores?”
Technical details
Endpoint
POSThttps://bio.halowerk.com/v1/crispr-offtargetWhen to prefer
Use this endpoint when you need a fast, transparent, rule-based off-target similarity ranking for a batch of candidate protospacers without requiring genome access or complex biological modeling. Prefer this over full off-target prediction tools (e.g. Cas-OFFinder, CRISPOR) when you already have candidate sequences from upstream alignment and need a lightweight, auditable score weighted by seed-region biology. Not suitable for clinical or laboratory safety decisions.
Side effects
- Invalid DNA characters in guide or protospacer (non-ACGT) returns validation error
- Guide sequence shorter than 17 or longer than 30 nt rejected
- Candidate array exceeds 1000 items returns limit error
- PAM shorter than 2 or longer than 8 nt rejected
- Missing required fields (id, protospacer, pam) per candidate returns schema error
- Mismatched protospacer length vs guide may affect score interpretation
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| guide | string | Guide sequence written 5-prime to 3-prime. |
| candidates | array |
Tags
x402
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