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

With no annotations present, the description carries the full burden and does so well: it discloses cost (~12 credits, 0.6/result), billing behavior (empty results/failures never charged), cache semantics (free 24h hit with cache=true, default fresh), and output field shape (type, durationSeconds/durationText, UTC publishedAt).

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, all information-dense and non-redundant. The most important facts — what the tool does and what the output looks like — are front-loaded, followed by cost and cache behavior. No wasted words.

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?

Given there is no output schema and no annotations, the description covers the essential decision factors: purpose, return shape, cost, cache behavior, and failure billing. The parameter semantics are already fully documented in the schema, so nothing critical is missing for an agent to invoke this 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?

Schema coverage is 100%, so baseline is 3. The description adds meaningful nuance beyond the schema by linking limit to per-result billing, clarifying that cache=true produces a free hit on a 24h cache, and noting that empty/failed results are not charged — all directly relevant to how q and limit behave.

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 states a specific action and resource: 'Rumble keyword search' for video results. It distinguishes itself by noting the output shape is 'same video card shape as channel-videos', which orients the agent toward a list-style search result rather than a single-video detail endpoint.

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 implies usage through 'keyword search' and gives useful cache guidance, but it never explicitly says when to choose this over siblings like rumble_channel_videos or rumble_video_details. No when-not-to-use or alternative routing is provided.

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