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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description adds real value beyond that: the returned user_id is the Keycloak 'sub' claim and the same identifier injected as user_id on workspace-scoped tool calls via request context — a non-obvious cross-tool invariant. It does not cover failure modes (e.g., unauthenticated session), which keeps it from a 5.

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?

Front-loaded with the core purpose in the first sentence, then when-to-use, then identity semantics. The trailing 'Returns' block partially restates what the output schema already provides, which is slight redundancy, but no sentence is truly wasted.

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 zero-param, read-only tool with an output schema and full annotation coverage, the description supplies everything an agent needs: purpose, trigger conditions, and the meaning/linkage of the returned identifier. Return-value detail is arguably redundant given the output schema, so nothing is missing.

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?

Zero parameters, so the baseline is 4. The description usefully explains the semantics of the value involved (requestor identity as Keycloak subject), which is more than the empty schema can convey, though there are no parameter names or formats to document.

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+resource (get the logged-in/requestor user for this MCP session) and immediately clarifies scope as 'requestor' rather than an arbitrary user, which separates it from siblings like get_user_by_email, get_user_profile, and get_current_workspace. An agent can select it without opening the schema.

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?

Explicitly enumerates when to call: the user asks 'who am I?', a workflow needs the current user's ID, or before tools that act on behalf of the requestor (intro requests, relationship actions, workspace membership checks). This is a genuine when-to-use list with concrete examples naming downstream sibling tool families.

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