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

Annotations already cover read-only, idempotent, non-destructive and open-world traits, so the description's job is to add context. It does so by disclosing the derivation method and, importantly, flagging that the output is HEURISTIC rather than authoritative — a meaningful reliability signal. It stops short of describing rate limits, pagination, or output shape.

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?

Two sentences, front-loaded with the core capability and the method, with the disclaimer trailing. Efficient and free of padding, though the 'not investment advice' clause is somewhat boilerplate.

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 usefully previews what comes back (levels plus latest close) and characterizes reliability. For a two-parameter read-only tool this is nearly complete; only return format or ordering details are missing, which is minor.

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 parameters (symbol, lookback_days with its 20-500 range and default 180) are fully documented in the schema. The description's phrase 'recent daily pivots' loosely gestures at the lookback window but adds no syntax or format detail beyond the schema, 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?

States a specific verb and resource ('Return key support/resistance price levels for a US ticker') and even discloses the derivation method (swing highs/lows, round-number levels) plus the inclusion of the latest close. It is clearly distinct from siblings like stock_quote or stock_history, though it never names an alternative.

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?

The only guidance is the disclaimer 'for research, not investment advice,' which is a liability caveat rather than usage direction. It never says when to reach for this tool versus candlestick_signals, bounce_scanner, or stock_history, leaving selection entirely to inference.

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