whoami

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the burden of behavioral disclosure. It reveals concrete behavior by listing the resolution sources: env, messaging socket, or a unique live cwd match. This is useful context, though it does not discuss failure modes or exact return format.

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?

The description is two short sentences, front-loaded with the core purpose and followed by a concise explanation of the resolution mechanism. Every word earns its place with no repetition or filler.

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 simple no-parameter tool, the description is largely complete: it states the tool's purpose and the sources it uses to resolve identity. It does not specify the exact return shape or error behavior, but these gaps are minor for this tool's low complexity.

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?

The tool has zero parameters, so the rubric baseline is 4. The description does not conflict with the empty input schema and there are no parameter semantics to explain.

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 what the tool does: 'Who this MCP connection is running as.' It then adds a specific verb and method, 'Resolves session id from env, messaging socket, or a unique live cwd match,' which distinguishes it from sibling session-related tools like get_session and list_sessions.

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 implies the tool is used when an agent needs to know the current connection's identity, but it does not explicitly state when to use it versus alternatives or provide exclusion criteria. The resolution-source detail provides some context, but no direct routing guidance is given.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.