# Sequence reverse complement

- Human page: https://happytails.ai/en/developer-tools/sequence-reverse-complement/
- Markdown: https://happytails.ai/en/developer-tools/sequence-reverse-complement.md
- Structured JSON: https://happytails.ai/agents/en/developer-tools/sequence-reverse-complement/index.json
- Visibility: public

## Tool capabilities

| Property | Value |
| --- | --- |
| Tool ID | `sequence-reverse-complement` |
| Category | developer-tools |
| Implementation | Registered implementation. Registration alone is not a production-quality guarantee. |
| Browser execution | Use the visible action or interactive controls. |
| Browser processing | Browser; see tool notes for network behavior. |
| HTTP API | Not callable through HTTP. |
| Browser-agent interface | run_current_tool |

### Implementation notes

Reverse-complements every FASTA record using the complete IUPAC DNA or RNA ambiguity alphabet. DNA uses A/T and RNA uses A/U. Case and optional - gaps are preserved; gaps reverse with the sequence. Original identifiers and full headers are retained. Header annotations and biological feature coordinates are not rewritten. This does not translate proteins or infer the biological strand. Runs locally without uploads or database lookup. Limit: 500000 combined input characters, 2000 records, 2000 validation issues, a 1000-symbol motif, 20000 matches and 10000000 symbol comparisons. Exceeding a limit rejects the complete report. Each export is limited to 3000000 characters; typed CSV allows 200000 values. Preview shows 200 rows. Processing stops after 10 seconds.

### Inputs and settings

Text input: Your text.

Example or placeholder shown in the interface (not a validated fixture):

```text
Type or paste your input…
```

Up to 500,000 characters. Review the settings before running.

| Setting | Meaning | Control type | Default | Constraints |
| --- | --- | --- | --- | --- |
| `alphabet` | Sequence alphabet | select | "dna" | Allowed: dna, rna |
| `allowGaps` | Allow alignment gaps (-) | select | "false" | Allowed: false, true |

### Browser-agent workflow

1. Open the human page in a browser that supports WebMCP.
2. Discover the interface exposed by that page; use its actual schema.
3. Select files on the page first when the tool requires files.
4. Call `run_current_tool` with valid input and settings.
5. Inspect the returned result or error and the displayed output. Retrieve files from the displayed download links.

Calls do not automatically copy or download results. Browser permissions still apply. Interface availability alone is not proof of successful execution.

### Planning specification

Reverse-complements every FASTA record using the complete IUPAC DNA or RNA ambiguity alphabet. DNA uses A/T and RNA uses A/U. Case and optional - gaps are preserved; gaps reverse with the sequence. Original identifiers and full headers are retained. Header annotations and biological feature coordinates are not rewritten. This does not translate proteins or infer the biological strand. Runs locally without uploads or database lookup. Limit: 500000 combined input characters, 2000 records, 2000 validation issues, a 1000-symbol motif, 20000 matches and 10000000 symbol comparisons. Exceeding a limit rejects the complete report. Each export is limited to 3000000 characters; typed CSV allows 200000 values. Preview shows 200 rows. Processing stops after 10 seconds.

This describes intended requirements. Use the implementation notes, interface schema and observed output to determine current support.

### Complete machine-readable capability record

```json
{
  "id": "sequence-reverse-complement",
  "category": "developer-tools",
  "built": true,
  "requirements": "Reverse-complements every FASTA record using the complete IUPAC DNA or RNA ambiguity alphabet. DNA uses A/T and RNA uses A/U. Case and optional - gaps are preserved; gaps reverse with the sequence. Original identifiers and full headers are retained. Header annotations and biological feature coordinates are not rewritten. This does not translate proteins or infer the biological strand. Runs locally without uploads or database lookup. Limit: 500000 combined input characters, 2000 records, 2000 validation issues, a 1000-symbol motif, 20000 matches and 10000000 symbol comparisons. Exceeding a limit rejects the complete report. Each export is limited to 3000000 characters; typed CSV allows 200000 values. Preview shows 200 rows. Processing stops after 10 seconds.",
  "implementation": {
    "fields": [
      {
        "key": "alphabet",
        "label": "Sequence alphabet",
        "value": "dna",
        "type": "select",
        "values": [
          "dna",
          "rna"
        ]
      },
      {
        "key": "allowGaps",
        "label": "Allow alignment gaps (-)",
        "value": "false",
        "type": "select",
        "values": [
          "false",
          "true"
        ]
      }
    ],
    "registrationFamily": "sequence-tools",
    "presentation": "metrics",
    "note": "Reverse-complements every FASTA record using the complete IUPAC DNA or RNA ambiguity alphabet. DNA uses A/T and RNA uses A/U. Case and optional - gaps are preserved; gaps reverse with the sequence. Original identifiers and full headers are retained. Header annotations and biological feature coordinates are not rewritten. This does not translate proteins or infer the biological strand. Runs locally without uploads or database lookup. Limit: 500000 combined input characters, 2000 records, 2000 validation issues, a 1000-symbol motif, 20000 matches and 10000000 symbol comparisons. Exceeding a limit rejects the complete report. Each export is limited to 3000000 characters; typed CSV allows 200000 values. Preview shows 200 rows. Processing stops after 10 seconds.",
    "inputMaxLength": 500000,
    "inputErrorCode": "SEQUENCE_INPUT",
    "example": {
      "input": ">sample unchanged description\nACGTrynACGT\n",
      "options": {
        "alphabet": "dna",
        "allowGaps": "false"
      }
    },
    "experience": {
      "automatic": false,
      "single": false,
      "inputMaxLength": 500000,
      "inputMode": "text",
      "label": "Your text",
      "placeholder": "Type or paste your input…",
      "help": "Up to 500,000 characters. Review the settings before running.",
      "action": null
    },
    "mode": "explicit",
    "interactive": false
  },
  "execution": "Browser interface",
  "api": null,
  "browser_agent": {
    "supported": true,
    "name": "run_current_tool",
    "discovery": "WebMCP on the human page in a supporting browser",
    "verification": "See audit/API-AUDIT.md; availability is not verification"
  }
}
```

## Page guide

Reverse-complement DNA or RNA FASTA sequences using every IUPAC ambiguity symbol, with original case and headers retained.

How can we improve this tool?

Report a problem or share an idea.

Please leave out private information. Your message and the tool name go to our team via PostHog.

### How to use Sequence reverse complement

1. Paste FASTA and choose DNA or RNA.
2. Enable literal gaps only for aligned input.
3. Review sequence lengths and download the reverse-complemented FASTA and report.

## Useful next steps

- [FASTA validator](https://happytails.ai/en/developer-tools/fasta-validator/) ([Markdown](https://happytails.ai/en/developer-tools/fasta-validator.md))

- [FASTA sequence extractor](https://happytails.ai/en/developer-tools/fasta-sequence-extractor/) ([Markdown](https://happytails.ai/en/developer-tools/fasta-sequence-extractor.md))

- [Sequence motif finder](https://happytails.ai/en/developer-tools/sequence-motif-finder/) ([Markdown](https://happytails.ai/en/developer-tools/sequence-motif-finder.md))

## Ambiguity codes are complemented

R and Y exchange, M and K exchange, B and V exchange, and D and H exchange. S, W and N remain themselves. DNA pairs A with T; RNA pairs A with U.

### Annotations are not transformed

Headers retain their original text. Biological feature coordinates in those headers are not updated, and no biological strand is inferred.