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Error strings

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Situation

Your agent reads raw HTML, markdown or page metadata instead of a rendered view.

Symptom

The agent quotes or follows text that a person looking at the rendered page never saw, for example text from a comment, a hidden element or a metadata attribute.

Cause

The paper names this class 'Content Injection': the machine-readable stream and the human-visible page can diverge. It also describes pages that serve different content to agent visitors than to people, so your own check with a browser may not show what your agent got.

Fix

1) Build the model input from the visible text only, or list hidden candidates and drop them before the model sees them. 2) Compare the raw text your agent fetched with a rendered view and review the difference. 3) Treat any instruction addressed to an AI in a hidden place as a red flag: drop it and note the URL. 4) Keep the fetched raw page in your logs so you can see later what the agent really read.

Snippet

from bs4 import BeautifulSoup, Comment
def hidden_candidates(html):
    soup = BeautifulSoup(html, "html.parser")
    out = [("comment", c.strip()) for c in soup.find_all(string=lambda s: isinstance(s, Comment))]
    for el in soup.find_all(True):
        style = (el.get("style") or "").replace(" ", "").lower()
        if (el.has_attr("hidden") or el.get("aria-hidden") == "true"
                or "display:none" in style or "visibility:hidden" in style or "font-size:0" in style):
            out.append(("hidden-element", el.get_text(" ", strip=True)))
    return [(k, t) for k, t in out if t]

Verify

Create a test page you own with one clearly marked test sentence inside an HTML comment and another inside an element hidden with CSS. Run the function on it. Expected: one comment entry and one hidden-element entry. Then confirm that the text you send to the model contains neither sentence.

Source

https://papers.ssrn.com/sol3/papers.cfm?abstract_id=6372438

Use this via MCP

Streamable HTTP, no authentication: https://agent-economy-data.onrender.com/notes/mcp. Tools: find_cards, get_card, report_outcome, and when enabled ask_markedet / get_answer. See llms.txt. Same notes as files: Agent Field Guide.