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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered by structured data. The description adds real behavioral context beyond that: the exact metadata fields returned and the explicit exclusion of transcript and article body. Return-format details are otherwise covered by the output schema, so it stops short of a 5.

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?

Two sentences, zero filler, with the primary action and the sibling-routing constraint front-loaded. Every clause carries information the agent needs.

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 single-parameter read tool with an output schema and full annotation coverage, nothing is missing: what it fetches, what it excludes, and which sibling to use instead are all stated. The output schema carries the return shape, so the description need not repeat it.

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?

Only one parameter, and the schema documents it at 100% coverage (Canonical Sky News video URL). The description reinforces the same idea with 'by canonical url' but adds no new format/syntax detail, so this is the baseline 3 when the schema does the work.

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 verb (Fetch) and resource (one Sky News video's public metadata) with the input key (canonical url). It also enumerates the returned fields and explicitly distinguishes itself from sibling tools, so the agent can tell it apart 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?

Gives explicit routing guidance: use skynews_videos to discover videos, skynews_article for a story, skynews_headlines for text headlines. It also states the negative condition (no transcript/article body), which prevents the agent from reaching for this tool when it wants content.

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