zulip

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. It effectively describes key behaviors: it's a lookup/search operation (implying read-only), it's used for verifying display names before mentions, and it operates case-insensitively. However, it doesn't mention potential limitations like rate limits or error handling.

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 perfectly structured and concise. The first sentence states the purpose, the second provides usage guidelines, and the 'Args:' section clearly documents the parameter with an example. Every sentence earns its place with no wasted words.

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's moderate complexity (single parameter lookup), no annotations, but with an output schema present, the description is nearly complete. It covers purpose, usage, and parameter semantics well. The output schema will handle return values, so the description doesn't need to explain those. A minor gap is the lack of explicit mention about what happens when no matches are found.

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, so the description must compensate. It fully explains the single parameter 'query' with clear semantics: 'Substring to search for (case-insensitive)' and provides an example 'e.g. "john", "smith"'. This adds substantial meaning beyond the bare schema.

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 tool's purpose: 'Look up a user's display name by substring before mentioning them.' It specifies the exact verb ('look up'), resource ('user's display name'), and method ('by substring'), and distinguishes it from sibling tools like 'get_user_info' by focusing on substring search for mentions.

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 explicit guidance on when to use this tool: 'Call this BEFORE using @**Name** in a message if you're not 100% sure of the exact display name.' It also explains the context ('Zulip mentions require an exact match'), making it clear when this tool is necessary versus alternatives.

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