Show HN: TinyFn – 500 deterministic utility APIs for AI agents (via MCP)

[tacoooooooo]

Hey HN,

I built TinyFn because LLMs are bad at the boring stuff — counting letters, validating emails, converting units. But they're even worse at things that are literally impossible for them: hashing, regex execution, UUID generation. An LLM will never produce a correct SHA256 hash.

TinyFn is a set of 500+ simple, deterministic utility endpoints that agents can call via MCP or plain REST.

The "strawberry" problem is the cliché example, but in practice the more painful version is agents confidently returning wrong regex matches, botched conversions, or "valid" email addresses that aren't. These are all things that should just be function calls, not LLM guesses.

Technically it's straightforward — each endpoint is a small deterministic function behind a REST API. The MCP layer lets Claude, Cursor, and other MCP-compatible clients discover and call them as tools automatically.

Free tier is 100 requests/month, no credit card needed. Would love feedback on which tool categories are most useful and what's missing.

[BrunoVT1992]

If you quickly want to validate a generated guid / uuid use this tool https://www.guidsgenerator.com/inspect It will tell you if it is a RFC compliant version and which version it is. So far in my opinion chatgpt is very capable at generating them.