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

Annotations already cover safety (readOnly, idempotent, non-destructive, closed-world), yet the description adds behavior the annotations cannot express: the $0.05 USDC-on-Base charge, the fact that unsupported tickers are not billed, and a free sampled alternative. Pricing and billing-failure semantics are exactly the kind of context that prevents a costly misfire.

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?

Three dense sentences, each carrying information an agent needs, with the trigger condition stated early. The cost figure is front-loaded ahead of what the tool actually returns, and the ticker enumeration repeats the schema enum, but neither costs much space.

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 an output schema, annotations and full parameter documentation already supplied, the description covers the remaining gaps: what the card contains, its cost, and its error behavior. It does not say how current the underlying data is or what happens if a company issued no guidance, which are minor for a single-parameter read 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 100% and the ticker enum already enumerates NVDA, AMD and INTC, so the description's ticker list is largely redundant with structured data. The only real addition is the 404/no-charge consequence for out-of-enum input, which is a small supplement over the schema baseline.

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 names a concrete comparison: each guided figure from a prior earnings release against the reported figure in the next 10-Q, flagged delivered/missed with EDGAR citations. That is a specific verb-plus-resource statement an agent can act on. It stops short of explicitly contrasting itself with the sibling get_guidance, so the boundary is inferred from wording rather than stated.

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?

"Call when you need whether a company delivered on the outlook in its prior earnings release" gives a clear trigger condition, and the description supplies an alternative access path (free sample over HTTP) plus an exclusion: other tickers return 404 with no charge. What is missing is guidance relative to sibling tools such as get_guidance or get_filing_delta, leaving the agent to guess which card to buy.

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