whoamiReturn the authenticated caller: the user id the token was issued for, the granted OAuth scopes, and the actor type. Use it to confirm which account the connector is signed in as and which scopes (and therefore which tools) you hold.
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
| Name | Required | Description | Default |
|---|---|---|---|
| scopes | Yes | Scopes granted to this token (sorted). | |
| user_id | Yes | ||
| actor_type | Yes |
Changes observed during successful MCP inspections.
Output schema / additionalPropertiesRemoved value: -trueOutput schema / descriptionAdded value: +"Output of `whoami` — the authenticated caller."Output schema / propertiesAdded value: +{
+ "actor_type": {
+ "type": "string"
+ },
+ "scopes": {
+ "description": "Scopes granted to this token (sorted).",
+ "items": {
+ "type": "string"
+ },
+ "type": "array"
+ },
+ "user_id": {
+ "type": "string"
+ }
+}Output schema / requiredAdded value: +[
+ "user_id",
+ "scopes",
+ "actor_type"
+]Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations declare readOnlyHint: true. The description adds value by detailing the returned fields (user id, scopes, actor type) and the purpose, which is beyond the annotations. No contradictions.
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 with no wasted words. The key information is front-loaded, and each sentence serves a distinct purpose (what it returns and when to use it).
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?
With no parameters and an output schema present, the description provides complete context: what the tool does, what it returns, and its use case. No gaps remain.
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?
There are no parameters; schema coverage is 100%. The description does not need to add parameter information, and the baseline for zero parameters is 4.
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 clearly states it returns the authenticated caller's user id, OAuth scopes, and actor type. It uses a specific verb ('Return') and resource ('authenticated caller'), and no sibling tool provides identity introspection, making it well-distinguished.
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?
The description explicitly says to use it to confirm which account the connector is signed in as and which scopes/tools are held. While it doesn't state when not to use, the context is clear for a simple identity check.
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.