> ## Documentation Index
> Fetch the complete documentation index at: https://docs.solvice.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Solution Explanation

> Understand why the solver made specific assignment decisions

The explanation endpoint provides detailed insights into your solution, including constraint violations and alternative assignment options.

## Enable Explanation

Add the explanation option to your request:

```json theme={null}
{
  "employees": [
    {
      "name": "Alice",
      "skills": [{ "name": "bar" }]
    },
    {
      "name": "Bob",
      "skills": [{ "name": "kitchen" }]
    }
  ],
  "shifts": [
    {
      "name": "shift-1",
      "from": "2024-03-06T08:00:00",
      "to": "2024-03-06T17:00:00",
      "skills": [{ "name": "bar" }],
      "min": 1,
      "max": 1
    }
  ],
  "options": {
    "explanation": {
      "enabled": true
    }
  }
}
```

## Solution Response

The solver assigns `shift-1` to `Alice` since she has the required `bar` skill:

```json theme={null}
{
  "score": {
    "hardScore": 0,
    "mediumScore": 0,
    "softScore": -1,
    "feasible": true
  },
  "assignments": [
    {
      "shift": "shift-1",
      "from": "2024-03-06T08:00:00",
      "to": "2024-03-06T17:00:00",
      "skills": ["bar"],
      "employee": "Alice"
    }
  ]
}
```

## Explanation Response

Request the explanation from `/v2/fill/explanation/{jobId}`:

```json theme={null}
{
  "score": {
    "hardScore": 0,
    "mediumScore": 0,
    "softScore": -1,
    "feasible": true
  },
  "conflicts": [
    {
      "constraint": "Employee Skill Level Match Soft",
      "score": "-1soft"
    }
  ],
  "unresolved": [
    {
      "constraint": "Employee Skill Level Match Soft",
      "score": "-1soft"
    }
  ]
}
```

<ResponseField name="conflicts" type="array">
  Individual constraint violations contributing to the score
</ResponseField>

<ResponseField name="unresolved" type="array">
  Aggregated constraints that could not be fully satisfied
</ResponseField>

## Alternative Assignments

When explanation is enabled, the solver evaluates all possible employee-shift combinations:

```json theme={null}
{
  "alternatives": {
    "shift-1": [
      {
        "shift": "shift-1",
        "employee": "Alice",
        "score": {
          "hardScore": 0,
          "mediumScore": 0,
          "softScore": -1,
          "feasible": true
        },
        "violations": [
          {
            "constraint": "Employee Skill Level Match Soft",
            "score": "-1soft"
          }
        ]
      },
      {
        "shift": "shift-1",
        "employee": "Bob",
        "score": {
          "hardScore": -1,
          "mediumScore": 0,
          "softScore": -1,
          "feasible": false
        },
        "violations": [
          {
            "constraint": "Employee Skill Match",
            "score": "-1hard"
          },
          {
            "constraint": "Employee Skill Match Soft",
            "score": "-1soft"
          }
        ]
      }
    ]
  }
}
```

<Info>
  The alternatives show that assigning Bob would violate a hard constraint (skill mismatch), explaining why Alice was chosen.
</Info>

## Explanation Options

<ParamField body="options.explanation.enabled" type="boolean" default="false">
  Enable post-processing to generate alternatives for each assignment
</ParamField>

<ParamField body="options.explanation.filterHardConstraints" type="boolean" default="false">
  Exclude alternatives that violate hard constraints from the response
</ParamField>

## Use Cases

| Scenario              | How Explanation Helps                            |
| --------------------- | ------------------------------------------------ |
| **Debugging**         | Identify why a solution is infeasible            |
| **User transparency** | Show managers why specific assignments were made |
| **What-if analysis**  | Evaluate impact of assigning different employees |
| **Constraint tuning** | Understand which constraints drive the solution  |

<Tip>
  Use `filterHardConstraints: true` to only see viable alternatives, reducing response size for large problems.
</Tip>