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

Annotations already mark this read-only, idempotent, and non-destructive. The description meaningfully adds behavioral context beyond annotations: per-call cost, wallet requirement, keyless Yahoo Finance backend, no rate limits in practice, and payment/auth options. No contradictions exist.

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?

The description is long but information-dense, covering scope, alternatives, backend, symbol formats, return shape, and payment instructions with no filler. It is front-loaded with the core purpose and usage, while later sentences provide operational context. Slight bloat from multiple payment delivery options slightly prevents a 5.

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?

Given the single parameter, rich annotations, output schema, and explicit alternative routing, the description is complete for safe and correct invocation. It even covers authentication/payment requirements, which is critical for a paid connector. An agent has everything needed to decide whether and how to call it.

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 single required parameter is fully documented in the schema with the same symbol format examples repeated in the description. The description adds no genuinely new parameter semantics beyond what the schema already states, so the baseline score of 3 is appropriate.

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 opens with a specific verb and resource: live stock/index/FX/crypto quote, and enumerates exact returned fields. It also distinguishes itself from named sibling tools (stock-history, premarket-quote, crypto-price), making its scope unambiguous.

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 description explicitly tells the agent when to use this tool versus alternatives: 'single-symbol NOW read' for quotes, stock-history for OHLC time series, premarket-quote for pre/post-market, and crypto-price for richer crypto fields. This is the gold standard for usage routing.

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