docs: add bedrock:CountTokens to IAM policy examples#1181
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Strands SDK uses bedrock:CountTokens to estimate token usage before model calls, enabling proactive context window management. Users running Strands-based agents need this permission in their IAM policies.
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Thanks for adding bedrock:CountTokens — it's a real pain point for Strands-based agents. The JSON is valid and the boundary-policy change looks good. A few things to resolve before merging:
- The addition to
iam-policy-user.jsondoesn't match the stated rationale (see inline comment). Strands runs inside the agent at runtime under the execution role, not under the developer's user credentials. docs/PERMISSIONS.mddescribes what each policy grants in prose; it now drifts out of sync with the updated JSON.- The PR description says this is the companion to a CDK constructs PR that adds
bedrock:CountTokensto theAgentCoreRuntimeexecution role — that change isn't onmaininagentcore-l3-cdk-constructsyet (src/cdk/constructs/components/primitives/runtime/AgentCoreRuntime.ts:74still lists onlyInvokeModel/InvokeModelWithResponseStream). Worth linking / coordinating so users following the docs aren't blocked by CDK-vended roles that still lack the permission.
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Summary
bedrock:CountTokensto bothdocs/policies/iam-policy-boundary.jsonanddocs/policies/iam-policy-user.jsonWhy
The Strands SDK calls
bedrock:CountTokensto estimate token usage before model calls, enabling proactive context window management. Users running Strands-based agents need this permission included in their IAM policies. Without it, token estimation fails silently.Related
Companion L3 constructs PR: https://github.com/aws/agentcore-l3-cdk-constructs/pull/213
Test plan