Free TierAPI Key Auth
ContentKing is an SEO monitoring and automated website auditing tool that tracks on-page SEO health, detects issues, and monitors search rankings in real-time.
#8 of 15 in Seo · #44 of 52 in Monitoring
Checklist Breakdown
12 of 33 checks passed.
14 unscored.
Can an agent find and understand this tool without a web search?
✗
Published OpenAPI/Swagger spec
✗
Has llms.txt or llms-full.txt
✗
Has an MCP server (official or well-maintained)
✗
MCP server listed in a public registry
✓
API reference docs are publicly accessible
✓
Docs include runnable code examples
✓
Has a public changelog or release notes
✓
Has a public status page
Can an agent create an account and get credentials without human intervention?
✗
Signup does not require CAPTCHA
✗
Signup does not require phone verification
✓
Supports API key auth (not only OAuth)
✗
API key obtainable without manual approval
✓
No mandatory billing info to start
✓
Can sign up without creating an organization
Can an agent operate autonomously without upfront payment or contracts?
✓
Has a free tier
✓
Usage-based pricing available
✓
No minimum contract or commitment
✓
Pricing page is public (no 'contact sales')
✓
Free tier sufficient for testing (not just a trial)
How well does the API work for non-human consumers?
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SDK available in 2+ languages
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Structured error responses (JSON with error codes)
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Idempotency support on write endpoints
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Pagination on list endpoints
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Webhook/event support
—
Sandbox or test mode available
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Rate limit headers in responses
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Consistent REST resource naming
Does the tool fail gracefully when an agent makes a mistake?
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Meaningful error messages (not just 500)
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429 responses include Retry-After header
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Documented uptime SLA (99.9%+)
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Graceful degradation under rate limits
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Request IDs in responses for debugging
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API versioning supported
Reviewer Notes
ContentKing lacks critical agent-native infrastructure: no MCP server, OpenAPI spec, or llms.txt documentation. While it offers an API with API key authentication and a free tier, account creation requires manual signup through their web interface. The API exists but appears minimally documented publicly, making discovery and integration challenging for autonomous agents. The main strength is the free tier availability; the primary weakness is the absence of structured, machine-readable API documentation and the inability to programmatically provision accounts.
Let your agents find tools like ContentKing
Install the Agent Native Registry MCP server. Your agents can search, compare, and score tools mid-task.
claude mcp add --transport http agent-native-registry https://agentnativeregistry.com/api/mcp