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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds value beyond that by stating the article is 'public' (no auth implied) and by naming the payload contents (metadata plus body paragraphs), which tells the agent what it will receive.

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 tight sentences, front-loaded with the purpose before the sibling routing. Minor redundancy in restating 'canonical' from the schema, otherwise no wasted text.

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?

An output schema exists, so return-value detail is not needed, and annotations carry the safety profile. For a single-parameter fetch tool the description covers purpose, scope, and sibling routing completely.

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?

There is a single url parameter with 100% schema description coverage ('Canonical MarketWatch article URL'). The description only echoes the word 'canonical', adding no format or validation detail beyond the schema, so the baseline 3 applies.

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 and resource ('Fetch public MarketWatch article metadata and body paragraphs') and immediately names the three sibling feed/section tools it is not. An agent can distinguish it from marketwatch_headlines, marketwatch_sections, and marketwatch_news without opening a 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?

Explicit routing guidance: use it for a single canonical URL article, and use marketwatch_headlines / marketwatch_sections / marketwatch_news for lists, browsing, and the general feed respectively. When-to-use and when-to-use-something-else are both spelled out.

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