# What is Tool Poisoning?

An attack in which malicious instructions are embedded in an MCP tool's description or metadata so an agent treats them as authoritative context and acts on them.

Source: https://usewire.io/glossary/tool-poisoning/
Last updated: 2026-04-30

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Agents read tool descriptions into the same context window they use for user prompts and retrieved documents. Anything in those descriptions is trusted by default. Attackers exploit this by hiding instructions, swapping descriptions after install, or registering near-duplicate tools, turning the tool registry into a persistent compromise channel. The MCPTox benchmark documented a 72.8% attack success rate across 20 production agents in 2025.

## Related terms

- [context-poisoning](https://usewire.io/glossary/context-poisoning/)
- [mcp](https://usewire.io/glossary/mcp/)
- [mcp-server](https://usewire.io/glossary/mcp-server/)
- [context-engineering](https://usewire.io/glossary/context-engineering/)
- [ai-agent](https://usewire.io/glossary/ai-agent/)