api-design

Name: api-design
Author: DevelopersGlobal

64stars10forks

How to install api-design?

developersglobal/ai-agent-skills/api-design

$npx -y skills add DevelopersGlobal/ai-agent-skills --skill api-design

Installs into the current project.

Summary

Design stable, versioned, self-documenting APIs. Easy to use correctly, hard to use incorrectly. Apply Hyrum's Law from day one.

Files · 1

View on GitHub

SKILL.md

1	## Overview
2
3	APIs are contracts. Once published, every behavior — documented or not — becomes something users depend on (Hyrum's Law). This skill enforces the discipline of designing APIs that are stable, self-documenting, and difficult to misuse.
4
5	## When to Use
6
7	- Creating any public API endpoint
8	- Designing function/library APIs
9	- Extending or versioning existing APIs
10
11	## Process
12
13	### Step 1: Design the Interface First
14
15	1. Write the usage examples before writing the implementation.
16	2. Ask: Is this easy to use correctly? Is it hard to use incorrectly?
17	3. Apply the principle of least surprise — the API should do what it looks like it does.
18	4. Design for the caller, not the implementer.
19
20	Verify: You can write 3 example usages without looking at the implementation.
21
22	### Step 2: Apply Hyrum's Law
23
24	5. Every observable behavior of your API will be depended upon by someone.
25	6. Document what IS and IS NOT guaranteed:
26	- Stable: return type, error codes, semantic behavior
27	- Unstable: response time, field ordering, internal implementation
28	7. Be conservative in what you expose — you can always add, never remove.
29
30	Verify: Every public field and behavior is either documented as stable or marked as internal.
31
32	### Step 3: Versioning Strategy
33
34	8. Version from day one: `/api/v1/`, `Content-Type: application/vnd.myapi.v1+json`
35	9. Breaking changes require a new version.
36	10. Maintain old versions for at least 6 months with deprecation notices.
37	11. Additive changes (new optional fields) are non-breaking.
38
39	Verify: API version is in the URL or headers. Deprecation policy is documented.
40
41	### Step 4: Self-Documentation
42
43	12. Every endpoint: purpose, inputs, outputs, error codes — documented.
44	13. Error messages tell the caller what went wrong AND how to fix it.
45	14. Schema validation on all inputs with meaningful error messages.
46	15. OpenAPI/Swagger spec generated (not hand-written).
47
48	Verify: A new developer can use the API from documentation alone, without reading source code.
49
50	## Common Rationalizations (and Rebuttals)
51
52	\| Excuse \| Rebuttal \|
53	\|--------\|----------\|
54	\| "We'll document it later" \| Undocumented APIs become black boxes. Document as you build. \|
55	\| "We can break it, it's internal" \| Internal APIs become external. Design them well from the start. \|
56	\| "Versioning is premature" \| Retrofitting versioning into an unversioned API is painful. Start versioned. \|
57
58	## Verification
59
60	- [ ] Interface designed before implementation
61	- [ ] Stable vs. unstable behaviors documented
62	- [ ] Versioning strategy in place
63	- [ ] All endpoints documented (OpenAPI/Swagger)
64	- [ ] Error messages actionable
65	- [ ] Breaking vs. non-breaking changes policy defined
66
67	## References
68
69	- [security-hardening skill](../security-hardening/SKILL.md)
70	- Hyrum's Law: https://www.hyrumslaw.com/

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api-design

64stars10forks

View on GitHub

How to install api-design?

developersglobal/ai-agent-skills/api-design

$npx -y skills add DevelopersGlobal/ai-agent-skills --skill api-design

Installs into the current project.

Summary

Design stable, versioned, self-documenting APIs. Easy to use correctly, hard to use incorrectly. Apply Hyrum's Law from day one.

Files · 1

View on GitHub

SKILL.md

1	## Overview
2
3	APIs are contracts. Once published, every behavior — documented or not — becomes something users depend on (Hyrum's Law). This skill enforces the discipline of designing APIs that are stable, self-documenting, and difficult to misuse.
4
5	## When to Use
6
7	- Creating any public API endpoint
8	- Designing function/library APIs
9	- Extending or versioning existing APIs
10
11	## Process
12
13	### Step 1: Design the Interface First
14
15	1. Write the usage examples before writing the implementation.
16	2. Ask: Is this easy to use correctly? Is it hard to use incorrectly?
17	3. Apply the principle of least surprise — the API should do what it looks like it does.
18	4. Design for the caller, not the implementer.
19
20	Verify: You can write 3 example usages without looking at the implementation.
21
22	### Step 2: Apply Hyrum's Law
23
24	5. Every observable behavior of your API will be depended upon by someone.
25	6. Document what IS and IS NOT guaranteed:
26	- Stable: return type, error codes, semantic behavior
27	- Unstable: response time, field ordering, internal implementation
28	7. Be conservative in what you expose — you can always add, never remove.
29
30	Verify: Every public field and behavior is either documented as stable or marked as internal.
31
32	### Step 3: Versioning Strategy
33
34	8. Version from day one: `/api/v1/`, `Content-Type: application/vnd.myapi.v1+json`
35	9. Breaking changes require a new version.
36	10. Maintain old versions for at least 6 months with deprecation notices.
37	11. Additive changes (new optional fields) are non-breaking.
38
39	Verify: API version is in the URL or headers. Deprecation policy is documented.
40
41	### Step 4: Self-Documentation
42
43	12. Every endpoint: purpose, inputs, outputs, error codes — documented.
44	13. Error messages tell the caller what went wrong AND how to fix it.
45	14. Schema validation on all inputs with meaningful error messages.
46	15. OpenAPI/Swagger spec generated (not hand-written).
47
48	Verify: A new developer can use the API from documentation alone, without reading source code.
49
50	## Common Rationalizations (and Rebuttals)
51
52	\| Excuse \| Rebuttal \|
53	\|--------\|----------\|
54	\| "We'll document it later" \| Undocumented APIs become black boxes. Document as you build. \|
55	\| "We can break it, it's internal" \| Internal APIs become external. Design them well from the start. \|
56	\| "Versioning is premature" \| Retrofitting versioning into an unversioned API is painful. Start versioned. \|
57
58	## Verification
59
60	- [ ] Interface designed before implementation
61	- [ ] Stable vs. unstable behaviors documented
62	- [ ] Versioning strategy in place
63	- [ ] All endpoints documented (OpenAPI/Swagger)
64	- [ ] Error messages actionable
65	- [ ] Breaking vs. non-breaking changes policy defined
66
67	## References
68
69	- [security-hardening skill](../security-hardening/SKILL.md)
70	- Hyrum's Law: https://www.hyrumslaw.com/

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