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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description still adds real value beyond them by disclosing the price point ($0.001), the point-in-time nature ("right now"), and the exact response contents; it stops short of rate limits or data freshness caveats.

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 front-loaded sentence that opens with the cost differentiator and then lists the payload. No filler; every clause adds information.

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 carries the return-value burden and does so by enumerating the fields. For a 2-parameter read-only tool that is nearly complete; only the relationship to sibling summary/explain tools is left implicit.

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% and the enum/default for window is fully documented in the schema, so baseline 3 applies. The description only implies the symbol scope ("one symbol") and says nothing about the window parameter that the schema does not already cover.

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?

Names a concrete resource (headline numbers for one symbol) and enumerates the returned fields (price, change, buy pressure, signal, event, confidence, trade count), so the agent knows exactly what it gets. It does not, however, distinguish itself from near-siblings such as market.summary or market.explain_move.

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)" gives an implicit routing hint — use this when cost matters and a full summary is not needed — but it never states when to prefer market.summary or other siblings over this one, nor any preconditions. Usage is implied rather than explained.

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