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

Annotations already declare readOnly/idempotent/non-destructive, and the description goes well beyond them: it discloses that each returned stock consumes one call against the daily limit (and that cross-category duplicates count once per category), tier gating (all tiers vs Pro-only AI fields), and a data-quality caveat that atr_pct is omitted when the volatility reading is missing or corrupted.

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 one-line definition followed by a well-structured bulleted parameter list; the Pro-tier paragraph slightly over-explains ('A big mover's price/volume/RSI alone doesn't say whether the move matters') but each element is relevant. Some return-field enumeration duplicates the output schema.

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 3-param, zero-required read tool with an output schema, the description covers everything an agent needs: category values and defaults, limits, market-cap filtering semantics, quota accounting, tier availability, and a hand-off to get_stock_research.

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 same quota/default/cap explanation appears verbatim in the schema for limit, category, and min_market_cap_b, so the description adds no semantics the schema does not already carry. Baseline 3 applies when the schema does the heavy lifting.

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?

Opens with a concrete verb+resource+scope ('Top market movers from the Stocklake universe - gainers, losers, most active') and enumerates the exact category values, which cleanly separates it from siblings like get_screener, get_market_pulse, or get_stocks.

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?

Clearly frames the scenario (surfacing big gainers/losers/most-active) and routes to the right next step for depth: 'For the full research bundle on any one mover, call get_stock_research(symbol).' It does not, however, state when to prefer a sibling scanner (e.g. get_screener) or exclusion conditions.

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