DeepSeek FIM (Fill-In-the-Middle)

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DeepSeek FIM (Fill-In-the-Middle) is a paid API for AI agents from DeepSeek at deepseek.mpp.paywithlocus.com, paid per call via MPP, Token dependent (~$0.003–$0.005) (dynamic), status unknown (last checked 2026-10-12).

Completes code at a cursor position by filling text between a given prefix (prompt) and suffix using DeepSeek's deepseek-chat model.

PriceToken dependent (~$0.003–$0.005)varies by input

Seller volume →—

Success—

StatusUnknown

How this service works

Code completion with fill-in-the-middle — provide a code prefix and optional suffix, and DeepSeek fills in the middle. Ideal for copilot-style code generation. Metered x402 supports deepseek-v4-pro.

Output

Returns a generated code string that fills the gap between the provided prompt (prefix) and suffix, completing the code at the cursor position as if writing the middle of a code block.

Example use cases

Example prompt

“Use DeepSeek FIM to fill in the missing code between this prefix 'def calculate_sum(a, b):\n ' and this suffix '\n return result' — generate up to 128 tokens with temperature 0.7.”

Technical details

Endpoint

POSThttps://deepseek.mpp.paywithlocus.com/deepseek/fim?utm_source=zero.xyz

When to prefer

Use this endpoint when you need to insert or complete code at a specific cursor location with known surrounding context (both prefix and suffix). Ideal for IDE-like code completion workflows, auto-fill tasks, or generating a function body when you already have the signature and closing structure. Prefer this over standard chat completions when the fill-in-the-middle pattern is required rather than open-ended generation.

Side effects

Model not supported: only deepseek-chat supports FIM; passing other model names returns an error
Missing required 'prompt' field causes a 400 validation error
Token limit exceeded if max_tokens is set too high for the plan
Rate limiting or quota errors if too many requests are sent
Empty or ambiguous prefix/suffix may produce irrelevant completions
Temperature out of valid range may cause parameter validation failure

Input

{
  "model": "deepseek-chat",
  "prompt": "def greet(name):\n    ",
  "suffix": "\n    return greeting",
  "max_tokens": 128,
  "temperature": 0.7
}

Schema · Request body

Field	Type	Description
modelrequired	string	Must be deepseek-v4-pro for metered x402 FIM
promptrequired	string	The code prefix to complete
suffix	string	The code suffix (text after the cursor). DeepSeek fills between prompt and suffix.
max_tokensrequired	number	Maximum tokens to generate (up to 384000). Required to bound metered x402 authorization.
temperature	number	Sampling temperature. Default: 1.

Output

{
  "data": {
    "id": "70da2686-2ed0-4cae-ba54-ce9ab626e56e",
    "model": "deepseek-v4-flash",
    "usage": {
      "total_tokens": 24,
      "prompt_tokens": 13,
      "completion_tokens": 11,
      "prompt_tokens_details": {
        "cached_tokens": 0
      },
      "prompt_cache_hit_tokens": 0,
      "prompt_cache_miss_tokens": 13
    },
    "object": "text_completion",
    "choices": [
      {
        "text": "greeting = f\"Hello, {name}!\"",
        "index": 0,
        "logprobs": null,
        "finish_reason": "stop"
      }
    ],
    "created": 1781064045,
    "system_fingerprint": "fp_8b330d02d0_prod0820_fp8_kvcache_20260402"
  },
  "success": true
}

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How this service works

Output

Returns a generated code string that fills the gap between the provided prompt (prefix) and suffix, completing the code at the cursor position as if writing the middle of a code block.

Technical details

Endpoint

POSThttps://deepseek.mpp.paywithlocus.com/deepseek/fim?utm_source=zero.xyz

When to prefer

Side effects

Model not supported: only deepseek-chat supports FIM; passing other model names returns an error
Missing required 'prompt' field causes a 400 validation error
Token limit exceeded if max_tokens is set too high for the plan
Rate limiting or quota errors if too many requests are sent
Empty or ambiguous prefix/suffix may produce irrelevant completions
Temperature out of valid range may cause parameter validation failure

Input

{
  "model": "deepseek-chat",
  "prompt": "def greet(name):\n    ",
  "suffix": "\n    return greeting",
  "max_tokens": 128,
  "temperature": 0.7
}

Schema · Request body

Field	Type	Description
modelrequired	string	Must be deepseek-v4-pro for metered x402 FIM
promptrequired	string	The code prefix to complete
suffix	string	The code suffix (text after the cursor). DeepSeek fills between prompt and suffix.
max_tokensrequired	number	Maximum tokens to generate (up to 384000). Required to bound metered x402 authorization.
temperature	number	Sampling temperature. Default: 1.

Output

{
  "data": {
    "id": "70da2686-2ed0-4cae-ba54-ce9ab626e56e",
    "model": "deepseek-v4-flash",
    "usage": {
      "total_tokens": 24,
      "prompt_tokens": 13,
      "completion_tokens": 11,
      "prompt_tokens_details": {
        "cached_tokens": 0
      },
      "prompt_cache_hit_tokens": 0,
      "prompt_cache_miss_tokens": 13
    },
    "object": "text_completion",
    "choices": [
      {
        "text": "greeting = f\"Hello, {name}!\"",
        "index": 0,
        "logprobs": null,
        "finish_reason": "stop"
      }
    ],
    "created": 1781064045,
    "system_fingerprint": "fp_8b330d02d0_prod0820_fp8_kvcache_20260402"
  },
  "success": true
}