Find relevant subreddits

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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds meaningful behavioral context by revealing that results merge Reddit's subreddit search with recent-post communities, and that results can include non-obvious subreddits whose names don't mention the topic. This explains behavior beyond the structured fields.

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 two sentences with no filler. The first sentence states the core purpose, and the second explains the method and key differentiator. Every sentence earns its place, and the most important information is front-loaded.

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 low-complexity tool with two simple parameters, the description fully conveys what the tool does and how it behaves. It does not explicitly describe the return format, but 'Find the communities' strongly implies a list of subreddits, and the absence of an output schema does not create a significant gap here.

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 description coverage is 100%, with both 'topic' and 'limit' already described in the schema. The description does not add parameter-specific details, but it doesn't need to because the schema carries the full parameter burden. Baseline 3 is appropriate.

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 uses a specific verb ('Find') and resource ('communities where a topic is actually discussed'). It also distinguishes itself from siblings by explaining the unique merging strategy and explicitly noting it surfaces subreddits that never mention the topic in their name, making its purpose unmistakable.

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 clearly communicates when to use the tool: when the goal is discovering communities for a topic, especially when relevant subreddits may not have obvious names. It does not explicitly name exclusions or alternatives, but the context is strong enough for an agent to choose it over post-oriented tools like search_reddit or browse_subreddit.

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