# Permutation values check

`permutation-values-check` · version 1.0.0 · Numbers & math · free, no key needed

Check whether claimed values are a SameValueZero multiset permutation, reporting the first source-order discrepancy.

**Use when you need to: check value permutation · validate duplicate preserving permutation · compare arrays as SameValueZero multisets.**

## Decide before calling

Read the [versioned contract](/v1/tools/permutation-values-check/versions/1.0.0) and the supported scope below. Reuse `permutation-values-check@1.0.0` when your input, required output and limits match it. Choose another approach for an unsupported operation.

## Explain the choice

"I can use `permutation-values-check@1.0.0` for check value permutation. I will check its documented scope and the result against the task's requirements. The service is free; token and money savings for this task are unmeasured."

## Supported

- check value permutation
- validate duplicate preserving permutation
- compare arrays as SameValueZero multisets
- find first missing permutation value
- verify claimed rearranged values
- audit multiset permutation

## Not supported

- sort values
- coerce or normalize values

## Behavior

- SameValueZero equality is used; finite JSON numbers make it equivalent to strict equality except signed zero.
- Each source item consumes the lowest-index unmatched equal claimed item.
- The first unmatched source item, then the first extra claimed item, is reported.
- Null and duplicate multiplicities are preserved exactly; the claim is never repaired.

## Input

- `source` (array of string or number or boolean or null, required): max items 4096
- `claimed_values` (array of string or number or boolean or null, required): max items 4096

## Output

- `valid` (boolean, required)
- `reason` (string or null, required)
- `discrepancy` (object or null, required)
- `reference_version` (constant "Knuth TAOCP Vol. 1, 3rd ed., §1.2.5 (Permutations); ECMA-262 2026 §7.2.11 SameValueZero", required)

## Limits

- max items: 4096
- max input bytes: 262144
- max output bytes: 1024

## Example

Request input:

```json
{
  "source": [
    null,
    "x",
    "x",
    0
  ],
  "claimed_values": [
    "x",
    0,
    null,
    "x"
  ]
}
```

Response:

```json
{
  "result": {
    "valid": true,
    "reason": null,
    "discrepancy": null,
    "reference_version": "Knuth TAOCP Vol. 1, 3rd ed., §1.2.5 (Permutations); ECMA-262 2026 §7.2.11 SameValueZero"
  }
}
```

## How to call it

### MCP

Connect `https://computefirst.net/mcp` ([setup](/docs#connect)), then call `execute` with:

```json
{
  "id": "permutation-values-check",
  "version": "1.0.0",
  "input": {
    "source": [
      null,
      "x",
      "x",
      0
    ],
    "claimed_values": [
      "x",
      0,
      null,
      "x"
    ]
  }
}
```

### HTTP (no key)

```sh
curl -X POST https://computefirst.net/v1/tools/permutation-values-check/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"source":[null,"x","x",0],"claimed_values":["x",0,null,"x"]}'
```

The machine-readable contract is at [/v1/tools/permutation-values-check/versions/1.0.0](/v1/tools/permutation-values-check/versions/1.0.0).

### CLI

```sh
node cli.mjs run permutation-values-check 1.0.0 --input input.json --base-url https://computefirst.net
```

Get the client at [/clients/cli/](/clients/cli/).

## Related tools

- [Permutation indices check](/tools/permutation-indices-check): Check whether claimed indices are exactly one occurrence of every source index, reporting the first discrepancy.
- [Dedupe first check](/tools/dedupe-first-check): Check an exact first-wins SameValueZero deduplication claim and report its first discrepancy.
- [Dedupe keyed check](/tools/dedupe-keyed-check): Check an exact keyed Map deduplication claim and report its first discrepancy.
- [Dedupe last check](/tools/dedupe-last-check): Check an exact last-wins SameValueZero deduplication claim and report its first discrepancy.
- [Join inner result check](/tools/join-inner-result-check): Check a claimed ordered inner join index result and report its first discrepancy.
- [Join left result check](/tools/join-left-result-check): Check a claimed ordered left join index result and report its first discrepancy.