Resolve an ENS name such as vitalik.eth to its Ethereum address.
Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.
{
"id": 1,
"jsonrpc": "2.0",
"method": "tools/call",
"params": {
"arguments": {
"name": "<name>"
},
"name": "ens"
}
}| Name | Required | Description | Default |
|---|---|---|---|
| name | Yes | ENS name, e.g. vitalik.eth |
Changes observed during successful MCP inspections.
Input schema / properties / nameAdded value: +{
+ "description": "ENS name, e.g. vitalik.eth",
+ "type": "string"
+}Input schema / requiredAdded value: +[
+ "name"
+]Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations supplied, the description carries the full behavioral burden. It discloses the core transformation but says nothing about failure behavior for unregistered or malformed names, name normalization, which chain is queried, or whether a network call/latency is involved. For a zero-annotation tool this leaves meaningful behavioral gaps.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
One sentence, zero waste, with the verb and the concrete example up front. Nothing is padding and nothing important is buried.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a one-parameter lookup with no output schema, the description correctly states the return type (an Ethereum address), which is exactly what an agent needs to plan a call. It falls short only on edge-case and failure semantics, which matter more here because no annotations are available.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, so the single `name` parameter is already documented, and the description merely repeats the same example. It adds no syntax details such as supported TLDs, subdomains, or normalization expectations beyond the schema baseline.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description names a specific verb ("Resolve") and resource ("ENS name") and states the concrete output (Ethereum address), with an inline example (vitalik.eth). No sibling tool covers ENS resolution, so differentiation isn't needed, but it also doesn't explicitly rule out look-alikes such as dns_lookup or crypto.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
Usage is implied by the input/output phrasing: an agent knows to call it when it has a name like vitalik.eth and wants an address. There is no guidance on when not to use it, whether mainnet-only or multi-chain, or what to do when resolution fails.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.