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

Annotations already declare readOnly, idempotent, non-destructive, so the safety profile is covered. The description adds real context beyond that: which asset classes are supported, that crypto requires the -USD pair form, and that fields like market cap/sector/earnings are conditional ('where they apply'). No auth or rate-limit detail, but that is minor given annotation coverage.

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?

Four sentences, front-loaded with the return payload and then the coverage boundaries. Dense and mostly earning its place, though the parenthetical enumeration of session states is slightly list-heavy.

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?

Output schema exists so return values need not be explained. The description covers supported asset classes, exclusion list, pair format, and example inputs — everything needed to invoke correctly, with only the instrument_id alternative 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%, so the baseline is 3. The description usefully adds crypto pair syntax ('BTC-USD') and multiple ticker examples beyond the schema's single 'AAPL' example, but it only discusses the ticker parameter and never mentions the alternative instrument_id UUID path.

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 ('Current snapshot of one instrument') and enumerates the exact fields returned (price, session state, 52-week range, market cap, sector, earnings date). This clearly separates it from siblings like get_price_history and get_technical_indicators, which cover different concerns.

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?

Explicitly bounds coverage: US-listed stocks, ETFs, major crypto (-USD pairs); excludes forex, futures, options, non-US listings. The 'current snapshot' framing implies when to choose it over historical tools, but no alternative sibling is named outright, so it falls short of a 5.

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