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

Annotations only give readOnlyHint/openWorldHint, but the description adds real behavioral context: quote cadence (5-minute for big stocks, hourly otherwise), the staleness caveat that it is not executable, and that the quote timestamp is included in the response. It stops short of auth/permission or rate-limit detail, so not a full 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?

Front-loaded with the core purpose and tightly written with no filler; the routing caveat is placed at the end where it belongs. Clauses are somewhat telegraphic ('US, or the home exchange's in dollars'), which costs a little readability.

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 shape itself (per-share price, gap %, lowest issuer, timestamp) and warns about freshness — enough to call it correctly. The remaining gap is ticker format, which neither the description nor the schema resolves.

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?

One parameter (tickers) with 0% schema description coverage; the description only restates the schema's maxItems ('Up to 12 tickers'). It never says whether entries are stock symbols, issuer tokens, or exchange-qualified identifiers, so it does not fully compensate for the coverage gap.

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 specific verb-and-resource ('Where a tokenized stock is cheapest'), enumerates the compared issuers (ST0x, Coinbase, Robinhood), and states the exact measure (per-share price for a $100 buy vs the stock's own price, gap %, lowest issuer). An agent can separate this from trade_link or fair_value 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?

Explicit when-not ('Not a live quote') paired with a named alternative and condition ('for an executable best-price buy use trade_link with usd'). This is a concrete routing rule rather than implied context.

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