Developer Reference Documentation — Writing Precise Technical Specifications

In this tutorial, you will learn about Developer Reference Documentation. We cover key concepts, practical examples, and best practices to help you master this topic.

Developer reference documentation provides precise specifications for APIs, libraries, and tools. It describes exactly what each function, parameter, and configuration option does. Unlike tutorials, reference documentation assumes the developer knows what they are looking for.

In this lesson, you will learn how to write reference documentation that developers can rely on for exact answers.

What You'll Learn

You will write precise function and API references, document parameters with constraints, and structure reference documentation for quick lookup.

Why It Matters

Developers consult reference documentation when they need an exact answer. Inaccurate or incomplete reference docs cause bugs and wasted time.

Real-World Use

DodaTech generates DodaZIP reference documentation from source code annotations. The auto-generated docs are verified by technical writers for clarity and consistency.

flowchart LR
  A[Reference Docs] --> B[Function Signatures]
  A --> C[Parameter Tables]
  A --> D[Return Types]
  A --> E[Error Codes]
  A --> F[Examples]
  B --> G[Developer Looks Up]
  A:::current
  classDef current fill:#f90,color:#fff,stroke:#333,stroke-width:2px

Function Reference Structure

Every function entry should include the complete signature with type annotations, a one-sentence description, all parameters with types and defaults, the return type and description, all exceptions that can be raised, and at least one usage example.

Keep descriptions concise. Reference docs are for lookup, not learning. Use consistent structure across all functions.

# Developer reference entry for compress_file

def compress_file(
    input_path: str,
    output_path: str | None = None,
    algorithm: str = "gzip",
    level: int = 6,
) -> CompressResult:
    """Compress a file using the specified algorithm.

    Args:
        input_path: Path to the file to compress. Must exist and be readable.
        output_path: Optional output path. Defaults to input_path with
            the algorithm extension appended.
        algorithm: Compression algorithm. Supported: gzip, bzip2, xz.
        level: Compression level 1-9. Higher is smaller but slower.

    Returns:
        CompressResult with fields: input_size, output_size, ratio, time_ms.

    Raises:
        FileNotFoundError: If input_path does not exist.
        ValueError: If algorithm is not supported.
        MemoryError: If compression buffer cannot be allocated.
    """

Parameter Documentation

Document every parameter with its name, type, whether it is required or optional, default value, accepted values or constraints, and a clear description.

Include value ranges, string formats, and enum options. Developers need to know exactly what values are valid.

Document interactions between parameters. If two parameters affect each other, explain how.

# Parameters for compress_file

| Parameter   | Type          | Required | Default | Description                       |
|------------|---------------|----------|---------|-----------------------------------|
| input_path | str           | Yes      | -       | Path to the file to compress      |
| output_path| str or None   | No       | None    | Custom output path                |
| algorithm  | str           | No       | gzip    | One of: gzip, bzip2, xz           |
| level      | int           | No       | 6       | Compression level 1-9             |

Common Mistakes

1. Incomplete Parameters

Missing parameters from documentation. Every parameter must be documented.

2. No Type Information

Not specifying parameter types. Developers must guess or read the source code.

3. Missing Defaults

Not documenting default values. Developers do not know what happens when they omit a parameter.

4. No Error Documentation

Only documenting success cases. Developers need to know what errors can occur.

5. Inconsistent Examples

Examples that use different conventions than the parameter documentation.

6. Outdated Signatures

Documentation that does not match the current code. Keep reference docs synchronized.

7. Vague Descriptions

A parameter called verbose described as Whether to be verbose. Describe what verbose output includes.

Practice Questions

1. What should every function reference entry include?

Signature, description, all parameters with types and defaults, return type, all exceptions, and examples.

2. Why document error cases?

Developers need to handle errors. Undocumented errors cause runtime failures.

3. How should parameter constraints be documented?

Value ranges, string formats, enum options, and dependency relationships between parameters.

4. Why use consistent structure across all reference entries?

Developers learn the pattern and can find information faster.

5. Challenge: Write a complete reference entry for a function you use. Include signature, parameters, return type, exceptions, and two examples.

FAQ

Mini Project

Select a library you use and audit its reference documentation. Evaluate three function entries for completeness. Rewrite any entries missing parameters, return types, error documentation, or examples.

What's Next

Next: SDK Documentation