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

Annotations already declare readOnly/idempotent/openWorld, so the safety profile is covered. The description adds what the annotations cannot: a cost model of 1 credit plus 3 credits per post returned, which is meaningful pre-call context. It does not mention failure modes (deleted/private posts) or rate limits, keeping it below a 5.

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?

A single sentence with the resource and return fields front-loaded, followed immediately by the cost. Nothing is padded and nothing needs reordering.

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 field enumeration compensates well for what the caller will receive, and the credit cost covers billing behavior. Minor gaps remain around error cases and whether media/embedded content is included, but the essentials for a correct call are present.

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 the id property already documents the permalink, redd.it, and t3_ accepted formats in detail. The description adds nothing about the id beyond the schema, so the 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 plus the exact fields returned (title, selftext, author, subreddit, score, numComments, url), which is far more precise than the title alone. It does not explicitly differentiate from near-siblings like lookup_reddit or search_reddit, so it falls short of a 5.

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 word 'one' and the required single id imply this is the by-ID retrieval path, but there is no explicit statement of when to use this versus lookup_reddit, search_reddit, or get_subreddit_posts. Usage is inferable rather than stated.

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