get_user_by_email

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

There are no annotations, so the description carries the full burden of behavioral disclosure. It only says 'Find a user by email' and does not explain what happens when no user matches, what fields are returned, whether the lookup is exact, or any error behavior. A read-only lookup is implied but not detailed.

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 one short, direct sentence with no redundant words. All necessary information for a simple one-parameter tool is front-loaded, and every word contributes to meaning.

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 tool with one fully documented parameter, the description is adequate for basic selection. However, with no annotations and no output schema, the agent still lacks information about return values, error cases, and matching semantics, so completeness is only minimally acceptable.

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%: the email parameter is already described as 'User email address'. The description's 'by email' phrasing adds no significant semantic detail beyond the schema, so the baseline score of 3 applies.

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 states a clear verb ('Find'), a resource ('a user'), and a specific lookup method ('by email'). This distinguishes it from siblings like get_user and get_current_user, which access users through different identifiers or contexts.

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 this tool should be used when you have a user's email address, but it gives no explicit guidance on when not to use it or when to prefer alternatives like get_user, get_users, or get_current_user. The usage context is only inferred from the wording.

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