get_user_by_screen_name

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

With no annotations provided, the description carries the full burden of behavioral disclosure. 'Fetches' implies a read operation, but it doesn't specify whether this requires authentication, rate limits, what data is returned, or error conditions. The description is minimal and lacks important behavioral context.

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 extremely concise at just 5 words, front-loading the essential information with zero wasted words. Every word earns its place in conveying the core functionality.

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?

Given the tool has an output schema (which handles return values) and only one parameter, the description's minimalism is somewhat acceptable. However, as a read operation with no annotations, it should ideally mention authentication requirements or data scope. The presence of an output schema raises the baseline, but the description remains sparse for a user lookup tool.

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 schema has 0% description coverage, but the description adds minimal context by mentioning 'screen name' as the lookup key. However, it doesn't explain what constitutes a valid screen name (format, length, character restrictions) or provide examples. With only one parameter, the baseline is higher, but the description doesn't fully compensate for the schema's lack of documentation.

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 the action ('fetches') and resource ('a user by screen name'), making the purpose immediately understandable. It doesn't specifically differentiate from sibling tools like 'get_user_by_id' or 'get_user_profile', but the verb+resource combination is unambiguous.

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 provides no guidance on when to use this tool versus alternatives like 'get_user_by_id' or 'get_user_profile'. It doesn't mention prerequisites, limitations, or context for choosing this specific user lookup method.

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