VidLens

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

Exceptional disclosure given no annotations: specifies return value 'asset manifest entry with file path', performance characteristics '[~30-120s]', side effects 'downloads media', and negative capability 'Does NOT perform visual indexing'. Covers timing, output format, and mutation behavior comprehensively.

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?

Perfectly structured four-sentence description: purpose (sentence 1), return value (2), sibling differentiation (3), performance metadata (4). Zero waste, front-loaded with critical information, appropriate density for complexity.

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?

Comprehensive for a download utility: covers I/O behavior, performance expectations, and sibling distinctions. Missing only minor lifecycle context (relationship to removeMediaAsset for cleanup) and storage persistence policies, but complete for invocation decision.

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 has 100% description coverage with detailed enum descriptions ('best_video = highest quality video+audio'). Description provides semantic context mapping to 'video, audio track, or thumbnail' but largely mirrors schema content. Baseline 3 appropriate when schema carries full documentation burden.

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?

Excellent specificity with clear verb 'Download', explicit resources 'YouTube video, audio track, or thumbnail', and destination 'local storage'. Distinguishes from siblings like indexVisualContent and importVideos through explicit scope definition.

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?

Strong differentiation via 'Does NOT perform visual indexing — this is honest file storage', clearly signaling this is distinct from indexVisualContent sibling. However, lacks explicit guidance on when to use versus importVideos or importPlaylist siblings which also handle video ingestion.

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