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

Annotations already cover readOnly, openWorld and destructive=false, so the description's job is additive, and it delivers: pricing ($0.01/call, first 25 free, failed calls free) and the explicit note that repeats are not free, which explains the idempotentHint=false in practical terms. It stops short of describing result shape or matching behavior (fuzzy vs exact, ambiguity handling), which matters for a name-based 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?

Front-loaded with the purpose, then usage routing, then the example, then cost. Every element is relevant, though the pricing sentence is dense and could be trimmed since cost is billing rather than selection guidance.

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 single-parameter read-only lookup with no output schema, the description covers purpose, sibling routing, returned fields, and cost model. An agent has everything needed to decide to call it and to expect a charged, side-effect-free symbol lookup.

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 schema already documents q with an example, so the baseline is 3. The description adds only a slight amount beyond it — extending eligible entity types to include crypto and providing the same q=volvo example — without clarifying match semantics or partial-name behavior.

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 ('find the ticker symbol') plus the accepted entity types (company, fund, index, crypto) and the fields returned (exchange, type, sector, industry). It explicitly positions itself against the siblings stock_quote and stock_history, so an agent can separate them without opening any 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?

Gives a clear trigger condition — 'use before /stock/quote or /stock/history when you only have a company name' — and a second distinct use case, finding a company's listings across several exchanges. The alternative tools are named rather than left to inference.

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