Get a user

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

With no annotations, the description carries the full behavioral burden. 'Provider-shaped, with provider-form ids' vaguely hints that the returned object and its id format depend on the provider, but it does not explain not-found/error behavior, auth requirements, or what the response actually looks like for each provider.

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 short sentences, front-loaded with the action and lookup key. Every word is doing work, though 'Provider-shaped, with provider-form ids' is jargon that is concise but not fully self-explanatory.

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 two-parameter lookup with no annotations and no output schema, the description is minimally adequate: it identifies the key and hints at provider variance. It omits what happens when the user is not found and leaves the meaning of 'provider-form ids' unexplained, so an agent lacks confidence about return shape and failure modes.

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 only 50%: login is documented in the schema, while the 21-value provider enum has no prose. The phrase 'provider-shaped, with provider-form ids' does add meaning to the provider parameter by signaling that id formats vary by provider, partially compensating for the missing enum description.

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 ('Fetch a user') plus the lookup key ('by login/username'), so the operation is unambiguous. No sibling tool returns users, so sibling differentiation is not needed here, but the description never references its relationship to the list/get family around it.

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?

There is no when-to-use, when-not-to-use, or alternative guidance. The verb implies a simple lookup, but nothing tells the agent under what circumstances to reach for get_user versus another orient/snapshot-style tool, nor what prerequisites (auth, valid provider) apply.

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