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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered. The description adds genuinely new context beyond them: the price point ($0.001) and the fact that it reflects the state 'right now', which helps an agent judge cost and freshness.

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?

A single tight sentence with the cost hook front-loaded and the returned fields following. Every clause carries information; no filler.

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?

There is no output schema, but the description compensates by enumerating the fields returned (price, change, buy pressure, signal, event, confidence, trade count). Combined with read-only annotations and full schema coverage, an agent has enough to invoke it correctly.

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 both symbol and window (with enum and default) are already fully documented in the schema. The description adds no parameter-level detail beyond what the schema provides, 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?

The description gives a specific verb+resource ('headline numbers of one symbol right now') and enumerates the returned fields, so the agent knows exactly what it gets. It does not, however, explicitly differentiate itself from the sibling market.summary, which likely returns overlapping headline metrics.

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?

'Cheapest call ($0.001)' and 'right now' imply a cost-conscious, single-symbol, real-time use case, which hints at selection criteria. But no alternative is named and there is no explicit when-to-use / when-not-to-use guidance versus market.summary or news.symbol.

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