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

Goes well beyond the readOnly/openWorld/idempotent annotations: it discloses that data may be delayed, that the tool is paid via x402 USDC on Base at $0.002 per successful call, and that an unpaid call returns a PaymentRequired object. Payment and latency behavior are exactly the traits annotations cannot express.

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 use case, then return fields, then the search-first caveat, then pricing — a sound ordering with no filler sentences. The inline ticker catalog is long and partly duplicates the schema examples, slightly diluting density.

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 carries the return-shape burden and does so fully: price, previous close, change (absolute and percent), day high/low, volume, 52-week range, exchange, currency, instrument type, market time and a source link. Combined with the payment and delay notes, an agent has everything it needs to call and interpret this tool.

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 already 100%, so the baseline is 3. The description adds value by demonstrating the breadth of accepted symbol formats across asset classes and venues (7203.T for Tokyo, VOW3.DE for Xetra, ^GSPC, EURUSD=X, GC=F), though it largely overlaps the schema's own examples.

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 precise verb+resource — 'latest market price of a listed instrument' — and enumerates the instrument classes (stock, ETF, index, FX, crypto) it covers. It is clearly distinguishable from siblings like history and search, which the description itself routes away from.

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?

Opens with an explicit trigger ('Use when an agent needs the latest market price'), and names an alternative workflow: 'Use /v1/search first if you only know the company name.' Together these tell the agent both when to use this tool and when to use another one first.

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