Call state-changing contract functions. Auto-fetches ABI. DRY_RUN default — pass confirm='CONFIRMED' to execute. Requires EVM_PRIVATE_KEY.
Part of the Kosyak Evm MCP server. Enforce policies on this tool with Intercept, the open-source MCP proxy.
AI agents use write_contract to create or modify resources in Kosyak Evm. Write operations carry medium risk because an autonomous agent could trigger bulk unintended modifications. Rate limits prevent a single agent session from making hundreds of changes in rapid succession. Argument validation ensures the agent passes expected values.
Without a policy, an AI agent could call write_contract repeatedly, creating or modifying resources faster than any human could review. Intercept's rate limiting ensures write operations happen at a controlled pace, and argument validation catches malformed or unexpected inputs before they reach Kosyak Evm.
Write tools can modify data. A rate limit prevents runaway bulk operations from AI agents.
tools:
write_contract:
rules:
- action: allow
rate_limit:
max: 30
window: 60See the full Kosyak Evm policy for all 43 tools.
Agents calling write-class tools like write_contract have been implicated in these attack patterns. Read the full case and prevention policy for each:
Other tools in the Write risk category across the catalogue. The same policy patterns (rate-limit, validate) apply to each.
Call state-changing contract functions. Auto-fetches ABI. DRY_RUN default — pass confirm='CONFIRMED' to execute. Requires EVM_PRIVATE_KEY.. It is categorised as a Write tool in the Kosyak Evm MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Add a rule in your Intercept YAML policy under the tools section for write_contract. You can allow, deny, rate-limit, or validate arguments. Then run Intercept as a proxy in front of the Kosyak Evm MCP server.
write_contract is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the write_contract rule in your Intercept policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the Intercept policy for write_contract. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
write_contract is provided by the Kosyak Evm MCP server (kosyak-evm-mcp-server). Intercept sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Open source. One binary. Zero dependencies.
npx -y @policylayer/intercept