CountTokens

Source: src/AWS/Bedrock/CountTokens.ts

Runtime binding for bedrock-runtime:CountTokens — count the input tokens a Converse or InvokeModel request would consume, using the bound model’s tokenizer, without invoking the model (and without inference cost).

The binding grants the function bedrock:CountTokens scoped to exactly the bound models.

Only a subset of models support token counting, addressed by their BARE foundation-model id (e.g. anthropic.claude-haiku-4-5-20251001-v1:0) — Amazon Nova models and cross-region inference-profile ids are rejected with a ValidationException (“The provided model doesn’t support counting tokens”).

Counting Tokens

Count Tokens for a Converse Request

// init
const countTokens = yield* Bedrock.CountTokens(
  "anthropic.claude-haiku-4-5-20251001-v1:0",
);

// runtime
const result = yield* countTokens({
  input: {
    converse: {
      messages: [{ role: "user", content: [{ text: "Say hello." }] }],
    },
  },
});
const tokens = result.inputTokens;

Count Tokens for a Raw InvokeModel Payload

const result = yield* countTokens({
  input: {
    invokeModel: {
      body: JSON.stringify({
        messages: [{ role: "user", content: [{ text: "Say hello." }] }],
      }),
    },
  },
});