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

The annotation readOnlyHint=true is reinforced by the description, and the description adds a key behavioral detail: captions are returned only 'when available'. This discloses that the tool may not return results for videos without captions, which is beyond what annotations provide. However, it does not mention error behavior, output format, or rate limits, leaving some gaps.

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?

The description is two sentences and very concise. It front-loads the purpose and then clarifies input. However, the second sentence ('Accepts a video URL') is largely redundant with the schema parameter description, so it adds minimal value. The overall compactness is good, but the redundancy prevents a perfect score.

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 tool with a single parameter, no output schema, and simple semantics, the description covers the essential information: what it does and when it works. The 'when available' condition handles the main edge case. Missing details like output format or pagination are not critical given the tool's simplicity, but could have been more explicit.

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?

The input schema has 100% coverage with the parameter description 'Link to the Rumble video.' The description's phrase 'Accepts a video URL' adds no new semantic value beyond the schema. Since the schema already fully documents the parameter, a baseline score of 3 is appropriate.

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 clear verb ('Get'), resource ('captions for a Rumble video'), and a condition ('when available'). It is specific to Rumble videos, distinguishing it from the many similar transcript retrieval tools in its sibling set (e.g., youtube_video_transcript_get, tiktok_video_transcript_get). However, it does not explicitly name any alternative, so differentiation is implied rather than stated.

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 when to use the tool (when captions for a Rumble video are needed) but provides no explicit guidance on when not to use it, alternatives, or edge cases. Given the tool's single-purpose nature and the clarity of the name, this is adequate but lacks the explicit routing seen in high-quality definitions.

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