Returns what the server knows about the current MCP client: clientInfo captured during initialize, User-Agent, and any _meta fields sent with this request. Useful for debugging caller identification.
| Name | Required | Description | Default |
|---|---|---|---|
| _meta | No | Optional self-identification. Keys: agent (string), model (string), version (string). |
| Name | Required | Description | Default |
|---|---|---|---|
| note | No | ||
| session | No | ||
| meta_override | No | ||
| effective_agent | No |
Changes observed during successful MCP inspections.
Input schema / examplesAdded value: +[
+ {}
+]Output schema / propertiesAdded value: +{
+ "effective_agent": {
+ "type": "string"
+ },
+ "meta_override": {
+ "type": "object"
+ },
+ "note": {
+ "type": "string"
+ },
+ "session": {
+ "type": "object"
+ }
+}Output schema / (root)Previous value: -nullNew value: +{
+ "additionalProperties": true,
+ "type": "object"
+}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is fully covered. The description adds provenance the annotations cannot: clientInfo is captured at initialize time while User-Agent and _meta come from the current request, which tells the agent these values may differ in origin. It does not mention whether the fields can be absent.
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?
Two sentences, front-loaded with the return value, with no repetition of schema details. The trailing usage sentence is short and earns its place as the only guidance present.
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?
An output schema exists, annotations are rich, and there is a single optional parameter, so the description only needs to establish purpose and provenance — which it does. Only the absence of any statement about missing/unavailable fields keeps it below 5.
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 coverage is 100% and the nested _meta properties (agent, model, version) are documented in the schema itself. The description only adds that _meta is 'sent with this request' and is echoed back, which is marginal extra meaning — baseline 3 is appropriate when the schema does the heavy lifting.
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?
States a specific verb and resource ('Returns what the server knows about the current MCP client') and then enumerates exactly what comes back: clientInfo from initialize, User-Agent, and request _meta. No sibling tool overlaps with this capability, so an agent can identify it immediately.
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?
'Useful for debugging caller identification' gives an implied use case but never says when not to use it or what alternative exists. There are no problematic alternatives in the sibling list, so the cost is low, but the guidance stops short of explicit conditions.
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.