diff --git a/packages/pi-ai/src/providers/anthropic-shared.ts b/packages/pi-ai/src/providers/anthropic-shared.ts
index 342c3fa11..1e8f78f9b 100644
--- a/packages/pi-ai/src/providers/anthropic-shared.ts
+++ b/packages/pi-ai/src/providers/anthropic-shared.ts
@@ -473,7 +473,7 @@ export function buildParams(
 		params.temperature = options.temperature;
 	}
 
-	if (context.tools) {
+	if (context.tools && context.tools.length > 0) {
 		params.tools = convertTools(context.tools, isOAuthToken, cacheControl);
 	}
 
diff --git a/packages/pi-ai/src/providers/azure-openai-responses.ts b/packages/pi-ai/src/providers/azure-openai-responses.ts
index 9dac639d4..7067f728b 100644
--- a/packages/pi-ai/src/providers/azure-openai-responses.ts
+++ b/packages/pi-ai/src/providers/azure-openai-responses.ts
@@ -217,7 +217,7 @@ function buildParams(
 		params.temperature = options?.temperature;
 	}
 
-	if (context.tools) {
+	if (context.tools && context.tools.length > 0) {
 		params.tools = convertResponsesTools(context.tools);
 	}
 
diff --git a/packages/pi-ai/src/providers/openai-codex-responses.ts b/packages/pi-ai/src/providers/openai-codex-responses.ts
index fa130515b..9ff27b767 100644
--- a/packages/pi-ai/src/providers/openai-codex-responses.ts
+++ b/packages/pi-ai/src/providers/openai-codex-responses.ts
@@ -312,7 +312,7 @@ function buildRequestBody(
 		body.temperature = options.temperature;
 	}
 
-	if (context.tools) {
+	if (context.tools && context.tools.length > 0) {
 		body.tools = convertResponsesTools(context.tools, { strict: null });
 	}
 
diff --git a/packages/pi-ai/src/providers/openai-completions.ts b/packages/pi-ai/src/providers/openai-completions.ts
index a67f9219d..cdeabccbf 100644
--- a/packages/pi-ai/src/providers/openai-completions.ts
+++ b/packages/pi-ai/src/providers/openai-completions.ts
@@ -344,7 +344,7 @@ function buildParams(model: Model<"openai-completions">, context: Context, optio
 		params.temperature = options.temperature;
 	}
 
-	if (context.tools) {
+	if (context.tools && context.tools.length > 0) {
 		params.tools = convertTools(context.tools, compat);
 		maybeAddOpenRouterAnthropicToolCacheControl(model, params.tools);
 	} else if (hasToolHistory(context.messages)) {
diff --git a/packages/pi-ai/src/providers/openai-responses.ts b/packages/pi-ai/src/providers/openai-responses.ts
index d0e6222af..3e00f576c 100644
--- a/packages/pi-ai/src/providers/openai-responses.ts
+++ b/packages/pi-ai/src/providers/openai-responses.ts
@@ -156,7 +156,7 @@ function buildParams(model: Model<"openai-responses">, context: Context, options
 		params.service_tier = options.serviceTier;
 	}
 
-	if (context.tools) {
+	if (context.tools && context.tools.length > 0) {
 		params.tools = convertResponsesTools(context.tools);
 	}