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

Annotations already declare readOnly/idempotent/non-destructive/openWorld, and the description adds genuinely new behavioral context: suspended accounts return isSuspended: true with null counters, nonexistent accounts return 404, and each call costs 1 credit plus 1 per user returned. These are exactly the operational details annotations cannot express.

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?

Three sentences, front-loaded with purpose, then return fields, then edge cases and cost. Every sentence carries distinct information with no restatement of the name or title.

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?

With no output schema, the description carries the burden of explaining return values, and it does: the field inventory, the suspended-account shape, and the 404 case. For a one-parameter read tool, an agent has everything needed to call it and interpret the result.

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?

There is a single parameter with 100% schema description coverage ("Username without the `u/` prefix" plus a regex pattern), so the schema fully documents the syntax. The description never references the username argument, so it adds nothing on top of the structured field — baseline 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?

States a specific verb and resource ("Get a Reddit account's public profile") and enumerates the fields returned: karma, account age, moderator/Premium status, bio, follower count. That inventory clearly separates it from siblings like get_reddit_user_comments, get_reddit_user_posts, and get_x_user, which return content or other platforms.

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 phrase "the facts that tell a real, established account from a throwaway" gives a concrete use case that orients an agent toward vetting/trust decisions rather than content retrieval. It does not name alternatives (e.g. lookup_reddit, search_reddit) or state exclusions, so it stops short of full routing guidance.

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