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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so safety needs no restating. The description does add real value beyond them by disclosing the return contents (rates, sizes, limits, open fee, contracts) — significant since no output schema exists. It stops short of noting whether a missing symbol errors or returns empty, which matters for a ticker-keyed lookup.

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 sentence with no padding, which is appropriately sized for a one-parameter read. But 'from the shelf' is decorative wording that costs clarity rather than earning its place, and the useful content is buried mid-sentence rather than front-loaded.

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?

For a one-param read with full annotation coverage and full schema coverage, the description is close to sufficient — it tells the agent what comes back. Gaps remain on lookup-miss behavior and on how this differs from `markets`/`credit_markets`, which the agent must infer from sibling names alone.

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 coverage is 100% and the `symbol` parameter is well documented, including the ticker format and a pointer to `markets`. The tool description itself adds nothing about the parameter, so the baseline 3 applies — the schema is doing all the work.

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 conveys that this returns a single stock's market data and enumerates the payload (rates, sizes, limits, open fee, contracts), which is genuinely informative. However, there is no verb and the framing 'full line from the shelf' is metaphorical jargon an agent must decode. It also does not name the sibling `markets` as the list-all alternative the way the schema's parameter text does.

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?

Nothing in the description states when to use this versus `markets`, `prices`, or `credit_markets`. The singular 'One stock' hints at single-symbol lookup, but the routing hint ('markets lists every one') lives in the schema, not the description, so the agent gets no explicit usage rule from the text being scored.

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