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

Annotations already declare readOnly/idempotent/non-destructive, so the description is free to add real behavioral context: result count cap (up to 10), ordering (closest match first), the fields returned (citation frequency, members, data-page link), and, crucially, the inclusion threshold (50+ citations or 50+ verified comments) and exclusions (health, legal-help, adult communities). That is information an agent cannot get from the schema or annotations.

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?

One dense paragraph that front-loads the trigger, then moves to inputs, outputs and filtering rules. Every sentence carries information, though the output-detail clause is a long run-on that could be split for easier scanning.

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 one-parameter read tool with a full schema and an output schema, the description still supplies the non-obvious pieces: what gets returned, how it is ranked, and which communities are excluded. Nothing needed to call or interpret the tool is missing.

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% and there is a single parameter, so the baseline is 3, but the description goes further by showing the expected input shape with a concrete example ('AI writing tool for marketers') that clarifies how briefly and specifically to phrase the query.

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 ('Find subreddits for a product') and scopes it to a product, brand or niche. It is readily distinguishable from the singular sibling get_subreddit, which fetches one existing community.

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?

Gives an explicit trigger condition ('Use this when someone asks which subreddits ... fit a product') plus a second use case (finding where AI answers look for recommendations). It does not name the sibling get_subreddit or state when-not to use this, so the alternative routing is left implicit.

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