How to Evaluate a Free LLM API List Before Building on It

Use a free-API list to find candidates, then check the few you might actually use. The attractive number in a directory may be a temporary promotion, an old limit or a quota your account doesn't qualify for. A short list you have checked is more useful than dozens of uncertain options.

The OpenRouter Free plan entry on Coding Plans is one place to start checking a candidate’s listed conditions and official references.

For each candidate, find the current model ID, quota, data policy and what happens when access runs out. If one of those is missing, leave it as an unanswered question. Don't let a neatly formatted comparison table make the offer look more settled than it is.

Turn each row into an evidence record

Choose two candidates, not twenty. For each, save the official model page, pricing or quota page, data policy and the date checked. Record your account's effective limits separately from public examples.

Leave unknown fields visibly unknown. A blank is more useful than a remembered quota from a different model or an old screenshot.

Check the smallest limiting dimension

Suppose your application needs twenty short classification requests in one burst. A large monthly token allowance may not help if the per-minute request limit is too low. Conversely, a high request allowance may be unsuitable for large documents if the input-token rate is restrictive.

Google's Gemini API rate-limit documentation describes separate request and token dimensions, applies limits per project rather than per key, and directs users to AI Studio for active limits. This is why creating another key in the same project is not a capacity plan.

Write a representative workload before testing: expected burst size, typical input size, output size and acceptable delay. That lets you reject an unsuitable service without spending hours integrating it.

Verify data conditions before using real content

A column saying “does not train” is not a complete privacy review. Ask whether prompts are retained, whether human review can occur, what metadata is logged, and whether external tools have their own policies.

The Gemini API terms distinguish unpaid and paid services and include regional provisions. Do not copy a global privacy conclusion from a list without checking which terms apply to your account and location.

For a gateway, review both gateway and upstream policies. OpenRouter's provider logging documentation makes that distinction explicit. Also verify that your tier actually offers the controls you plan to rely on; generic API documentation does not prove an entitlement on every plan.

Start with synthetic examples. A test does not need customer email, confidential source code or production credentials to demonstrate whether structured output and error handling work.

Test capabilities, not just a greeting

A successful “hello” request proves that one call completed. It does not establish reliable tool calls, schema adherence or enough context for your agent.

Build a small test set around your use case. A classifier should handle an ambiguous sample and an empty value. A coding agent needs a representative file edit and a way to verify it. A tool-using workflow should receive an invalid argument and recover without inventing a successful tool result.

Record the exact model identifier and settings. If a router selects models dynamically, record the model actually returned when available. Do not average different routes together and call the result one model's performance.

Define the failure policy before launch

Decide what happens when the free route is unavailable. A hobby tool might ask the user to retry later. A scheduled task might queue work. A paid fallback should have an explicit budget and remain compatible with your data policy.

Do not retry a quota error continuously. Distinguish a temporary capacity failure from a depleted allowance and use the service's retry guidance. Keep enough information to explain the failure without logging raw private prompts.

Keep a dated note for each route you use and revisit it when errors, retirement notices or terms change. You don't need to maintain an encyclopedia of free models. You need a small set of options you understand, with a sensible response when one stops working.