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

Annotations already declare read-only, idempotent, non-destructive behavior, so 'Read-only' in the description is redundant. The genuinely additive note is that visibility depends on the connected account's plan, which explains why results may be partial. It says nothing about output shape or pagination.

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?

Front-loads the trigger conditions, then tool identity, then parameters, then the exclusion. Dense and mostly free of filler, though the parameter block reads as a run-on and repeats default values already in the schema.

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 three-optional-parameter read tool with no output schema, the definition covers when to call, when not to, and the meaning of each parameter. The only gap is a hint at what comes back (a list of video entries), which would help an agent plan follow-up calls.

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?

With zero schema description coverage, the description carries the full burden and mostly succeeds: niche format (slug or group from list_niches, comma-separated), sort option meanings including the non-obvious x_factor (views vs the author's usual), and a limit range of 1-50 with default 10. Only the enum values themselves restate the schema.

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 resource with scope: fast-growing reels from a trend feed, seen as the connected account. The final clause explicitly separates it from analyze_video, so an agent can distinguish it from siblings without opening the schema.

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?

Names concrete triggering intents (what's trending in a niche, content ideas, viral examples) and an explicit exclusion with the alternative named: 'Do not use for one specific video the user links to; analyze_video does that.' Nothing is left to inference.

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