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

Annotations already establish read-only, idempotent, non-destructive, and closed-world behavior, so the bar is lower. The description adds genuinely useful context beyond them by describing the shape of each returned story and its sentiment taxonomy, which no output schema provides.

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 compact sentences, front-loaded with what the tool returns and followed by the filter option. There is no redundant restatement of the tool name or padding.

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?

With no output schema, the description correctly compensates by describing the return payload, and the two optional parameters are fully covered by the schema. The remaining gap is the undefined freshness window behind "newest" — no time range is stated, which matters for a news tool — and no hint of the empty-result case.

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 description coverage is 100%, so the limit range and default are already documented, giving a baseline of 3. The description adds only marginal meaning by giving ticker examples including a class-share format (BRK.B), but explains nothing about how the ticker interacts with limit or what happens for an unknown ticker.

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 names a specific verb+resource ("newest US stock market stories") and describes the payload of each item (summary, sentiment, named companies, link). It does not explicitly distinguish itself from siblings like search_news or get_story, so it stops short of a 5.

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?

It states an optional narrowing mode ("only stories about one company by ticker"), which implies the default is an unfiltered latest feed. However, there is no statement of when to prefer this over search_news or get_story, leaving the routing decision to inference.

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