Modern documentation isn't just about what you publish—it's about how you maintain it. As product teams ship faster and APIs grow more complex, the approach to documentation becomes a strategic choice, not a technical afterthought.
Generated documentation pulls directly from API specifications like OpenAPI or Fern Definition, regenerating automatically whenever the spec changes. Manual documentation exists separately—in CMSs, wikis, or Markdown files—requiring human coordination to stay synchronized with code.
This post breaks down the differences between generated and manual documentation approaches, explores where each excels, and helps you determine which model (or hybrid) best aligns with your team's workflow and documentation needs.
TLDR:
- Generated docs sync automatically with API specs, eliminating drift
- Manual docs require coordination between code changes and content updates
- Only 10% of organizations fully document their APIs, creating integration friction
- Hybrid approaches work best: generate API references, manually author conceptual guides
- Fern generates API docs and SDKs from specs while supporting human-written tutorials
What generated and manual documentation mean for developer portals
Generated documentation treats the API spec as the single source of truth. Docs generate directly from OpenAPI, AsyncAPI, or similar files, and regenerate automatically whenever the spec changes. Nothing lives outside that spec file.
Manual documentation works differently. Content exists separately from code—in CMSs, wikis, or Markdown files—requiring manual updates to stay synchronized.
The core distinction comes down to synchronization. Generated approaches keep documentation coupled to the API definition itself. Manual approaches require coordination between code changes and documentation updates. Both methods have their place, but they solve different problems for different team structures and workflows.
How API drift creates documentation problems
API drift occurs when an API's behavior diverges from its documentation. A field that was once optional becomes required, an endpoint returns new status codes, or response schemas change while the documentation stays frozen.
Research indicates that only 10% of organizations fully document their APIs. When documentation falls out of sync, developers waste hours troubleshooting phantom issues, testing repeatedly, and submitting support tickets. The problem isn't their code—it's documentation promising one behavior while the API delivers another.
Outdated documentation burdens support teams and pulls engineers away from feature work. Each mismatch erodes trust in the developer portal and increases operational costs through lost developer hours, support escalations, and abandoned integrations. Manual documentation is especially prone to drift because it's not automatically linked to the API specification. Teams must coordinate updates across code and content, and inevitably fall behind.
The single source of truth advantage in spec-driven workflows
Spec-driven workflows solve synchronization by making the API specification the single source of truth. When an API is defined in OpenAPI, Fern Definition, or AsyncAPI, that file becomes the authoritative description of the API.
Changes flow automatically from spec to documentation. Adding a field updates the reference documentation, regenerates response examples, and updates SDK snippets across all supported languages. The documentation portal always shows the current state because it reads directly from the spec.
This automation eliminates human coordination. No manual updates or notifications required. Fern extends this further by generating both documentation and SDKs while automatically handling breaking changes and version bumps. Human-written guides still need manual updates, but core reference content stays accurate by default.
Maintenance burden comparison across documentation approaches
Manual documentation creates ongoing maintenance that grows with API complexity. Every endpoint change requires updating descriptions, examples, and code snippets, then verifying accuracy. For large APIs, teams can spend hours per release keeping docs current.
Coordination adds overhead. Engineers communicate changes, writers interpret them, and reviewers verify correctness—delaying updates at every step.
Generated documentation shifts the effort upfront. Accurate OpenAPI or Fern Definition files, generation pipelines, and CI/CD integration ensure docs update automatically with each spec change. Manual updates can take 4–6 hours per release; generated documentation takes minutes to review, with automation handling the rest.
Human oversight still matters for clarity, conceptual guides, and examples, but generated workflows eliminate repetitive tasks, freeing teams to focus on higher-value work.
Versioning and multi-version support
Generated documentation automatically tracks API changes and creates new doc versions from the spec. Multi-version support lets developers access documentation for current and past API releases without manual updates. All versions stay synchronized with the source of truth, eliminating drift across releases.
Fern automatically manages documentation versioning alongside your API. When the spec changes, Fern generates new documentation versions while preserving older releases for reference. Teams can host multiple versions simultaneously, so developers see content that matches the API version they're using. This keeps historical API behavior accurately documented without manual intervention.
Collaboration workflows: docs-as-code vs traditional CMS
Docs-as-code stores documentation in version control alongside API specifications. Developers commit spec and doc changes in the same pull request, letting code review catch both implementation errors and documentation gaps before merging.
Traditional CMS platforms separate docs from code, requiring coordination between writers and engineers. This separation creates lag where deployed APIs don't match published documentation.
Version control enables collaboration through simultaneous edits, merge conflict resolution, and clear change history. Docs-as-code integrates into existing developer workflows, letting engineers use familiar tools—Git, pull requests, and CI/CD pipelines—with minimal learning curve.
CI/CD integration for automated documentation deployment
CI/CD pipelines automate the path from code commit to production deployment. When documentation lives in the same repository as API specifications, it flows through the same automated checks and deployments. Integrating documentation into CI/CD speeds up development by 20% and cuts support tickets by 40%.
Generated documentation integrates naturally into continuous deployment. An engineer updates an OpenAPI spec and commits the change. The CI pipeline validates the spec, generates updated docs, runs tests, and deploys everything together. The API and its documentation ship as a single atomic unit.
Manual approaches interrupt this flow. Even with code deploying automatically, documentation requires separate publication steps. Someone exports content from the CMS, reviews changes, and manually publishes to the docs site. This manual gate delays documentation updates even when the API ships on time.
Fern connects directly to CI workflows through GitHub Actions or other pipeline tools. Each spec commit triggers regeneration of API reference documentation, code examples, and SDKs. The entire developer portal updates without human intervention, keeping documentation synchronized with every deployment.
When manual documentation makes sense for your team
Manual documentation covers content that specs cannot generate. Conceptual guides, tutorials, architectural decisions, migration instructions, and troubleshooting resources all require human authorship to provide context, examples, and explanations.
API references show what endpoints do; guides explain why and how to use them. For example, getting started guides curate the key endpoints for first API calls—something a spec alone cannot do.
Even spec-driven teams write manual content. Fern generates API references automatically while teams author conceptual guides in Markdown. The goal isn't choosing one approach over the other, but using generated documentation for reference material and manual writing for everything else. This lets teams focus on high-value explanatory content rather than transcribing API schemas.
Hybrid documentation architectures that combine both approaches
Most teams benefit from combining both approaches rather than choosing one exclusively. The optimal structure uses generated documentation for API reference content while maintaining manual control over guides and tutorials.
The file structure reflects this split. API specifications live in version-controlled openapi/ or definition/ folders. Documentation teams author conceptual content in separate docs/ directories using Markdown or MDX files. Both integrate into a single documentation site, but each follows its appropriate workflow.
Fern's configuration supports this hybrid model. The docs.yml file defines navigation that mixes auto-generated API sections with manually authored guides. Developers see seamless documentation combining spec-derived reference pages with human-written onboarding content. The underlying architecture separates concerns while presenting unified information.
This separation lets teams assign work appropriately. Engineers own the spec files that generate reference docs. Technical writers own tutorial and guide content. Neither group blocks the other, and both contribute through their areas of expertise.
How Fern delivers generated documentation with full automation
Fern reads OpenAPI or Fern Definition files and generates complete API references automatically. Every endpoint, schema, and authentication method documented in the spec appears in the developer portal without manual transcription.
Code snippets generate across nine languages simultaneously. When a spec changes, examples update in every supported language. Developers see current, working code regardless of which SDK they choose.
The API Explorer populates directly from spec definitions. Request parameters, headers, and authentication requirements all derive from the same source file that defines the API contract. Changes propagate instantly across reference docs, code examples, and interactive testing interfaces.
Fern handles versioning through configuration files that organize content and specs into separate versions. Teams can maintain multiple documentation versions without duplicating content manually.
Teams write conceptual guides in MDX files that sit alongside generated references. The docs.yml configuration combines both content types into unified navigation. Readers see seamless documentation while the underlying architecture keeps reference material synchronized and guides under direct authorship control.
Final thoughts on reducing documentation drift
Generated documentation cuts the manual work that creates inconsistencies between code and docs. Commit spec changes, and documentation regenerates across all versions and languages without human coordination. Developers can trust the reference material because it derives directly from the specification that defines your API contract. The time saved compounds with every release, freeing your team to focus on higher-value documentation work.
FAQ
What is the difference between generated and manual documentation?
Generated documentation creates docs directly from API specifications like OpenAPI, keeping content synchronized with code automatically. Manual documentation exists separately in CMSs or Markdown files, requiring manual updates whenever the API changes.
How does spec-driven documentation prevent API drift?
Spec-driven workflows use the API specification as the single source of truth. When you update the spec, the documentation portal automatically regenerates reference pages and SDKs to match the new behavior, eliminating synchronization lag.
Can you combine generated and manual approaches?
Yes, a hybrid structure is often optimal. You can generate API reference material from specs while authoring conceptual guides, tutorials, and best practices in Markdown files to provide necessary context.
How does CI/CD integration benefit your workflow?
By storing documentation alongside code, you can validate and deploy docs automatically through your existing pipelines. This keeps your documentation and API shipping as a single atomic unit.
When should you use manual documentation?
Manual documentation excels for content that requires human narrative, such as architectural decisions, migration guides, and complex tutorials. These sections provide context that an API specification cannot generate.
