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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so safety is covered. The description adds genuinely new behavioral context: a once-per-day scan cadence, a 10-credit cost, and graceful degradation via scan_skipped when the balance is too low. It stops short of describing ordering, staleness of results, or what happens on repeat calls within the same day.

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 short sentences, each carrying distinct information: what is returned, the cost/cadence constraint, and the low-balance failure mode. The core purpose is front-loaded with no filler.

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 does the right thing by naming key response fields (credits_remaining, scan_skipped) and the included reply draft. It leaves some gaps — the shape of a mention, sorting, and whether cached results are returned on repeat calls — but an agent has enough to invoke it correctly.

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 (limit) with 100% schema description coverage, including the default of 20 and maximum of 50. The description adds nothing about how limit interacts with the daily scan or credits. Per the rubric, full schema coverage sets the baseline at 3.

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 opens with a specific verb and resource: 'List Reddit threads for the saved keywords,' plus the notable inclusion of 'the latest reply draft.' The verb 'List' clearly separates it from the mutating sibling draft_reddit_reply, but the description never names that sibling or explicitly draws the line between listing mentions and acting on them.

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?

It implies when the tool is appropriate (to see threads for saved keywords) and gives a strong operational constraint: a scan runs at most once per day and costs 10 credits. However, there is no explicit statement of when NOT to use it versus draft_reddit_reply or get_reddit_settings, and no prerequisite (e.g., keywords must be configured) is stated.

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