AI Agent sends nested input, causing placeholder misconfiguration in tool (Perplexity)

[Natan_Souza]

Describe the problem/error/question

I’m using the AI Agent node along with a tool (Perplexity) in my workflow.
The problem is that the AI Agent wraps the tool input in a nested object, which causes issues with placeholder resolution in the tool node.

The tool expects:
{ “query”: “how old is bill gates” }

But the AI Agent sends:
{ “query”: { “query”: “how old is bill gates” } }

This breaks the placeholder configuration that expects a string (like {{query}}), resulting in a misconfiguration error.

What is the error message (if any)?

Error in sub-node ‘Perplexity’
Misconfigured placeholder: ‘query’

Please share your workflow

I’m happy to share a sample, but essentially:

• Trigger: Chat message received
• AI Agent node
  • Tool: Perplexity
  • Agent sends: { query: { query: “…” } }
• Perplexity tool node uses placeholder {{query}}, or {{query.query}} inside JSON

Share the output returned by the last node

{
“query”: {
“query”: “how old is Frei Gilson”
}
}

Expected:
{
“query”: “how old is Frei Gilson”
}

Information on your n8n setup

• n8n version: 1.85.4
• Database (default: SQLite): none
• n8n EXECUTIONS_PROCESS setting (default: own, main):
• Running n8n via (Docker, npm, n8n cloud, desktop app): docker
• Operating system: ubuntu

[mohamed3nan]

Hi @Natan_Souza,

Thanks for the detailed explanation. The issue seems to stem from a type mismatch between how the placeholder is defined and what the AI Agent actually sends.

Currently, your body is set like this:

{ "role": "user", "content": "{query}" }

This expects query to be a string, but the AI Agent wraps it in an object ({ "query": { "query": "..." } }), which breaks the placeholder resolution.

Here are two options you could try:

Option 1: Set the Placeholder Type to “Not Specified”
This allows the tool to accept an object instead of enforcing a string:

Option 2: Adjust the Request Body to Match the Object Structure
If you want to keep the type as “String”, update the body to reference the nested value directly:

{ "role": "user", "content": {query} }

This way, the placeholder resolves correctly even with the nested structure.

[interss]

How are you @Natan_Souza @mohamed3nan

The solution that the respected @mohamed3nan suggested is interesting. I also leave my contribution.

Check if the suggestions below make sense to you.

Edit the Perplexity node and go to the JSON Body field
Modify the placeholder {query} to {query.query}

Modified JSON body…

{
  "model": "llama-3.1-sonar-large-128k-chat",
  "messages": [
    { "role": "system", "content": "Only respond with information from verifiable and credible sources. Include source urls and event dates when possible" },
    { "role": "user", "content": "{query.query}" }
  ],
  "max_tokens": 500,
  "top_p": 0.9
}

I hope I helped in some way.

Big hug

[interss]

Once you’ve tested and resolved your situation, and don’t mind, please mark my previous post and @mohamed3nan post as the solution (blue box with check mark) so that this ongoing discussion doesn’t distract others who want to find out the answer to the original question. Thanks.

[Natan_Souza]

thanks a lot!

I just removed the quotation marks from the placeholder, and it worked! \o/