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

Annotations already cover readOnly/idempotent/non-destructive safety, lowering the burden. The description adds genuinely useful behavioral context beyond annotations: the dual-mode behavior (symbol vs. market-wide) and the 'upcoming and recent' scope. No side effects, pagination, or rate-limit info, but the output schema covers the return shape.

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 sentences with no filler: function statement, usage modes, and a demonstrative example. The example earns its place because it shows the symbol+date+key combination absent from the schema examples, though it is slightly redundant with the schema's own example field.

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 4-param read-only tool with full schema coverage, a rich output schema, and comprehensive annotations, the description covers everything needed to invoke it correctly. The only gap is not explicitly differentiating it from the similarly calendar-like sibling release_calendar_markets.

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%, so the baseline is 3; the description adds value on top by showing how parameters combine (symbol + from/to together), rephrasing the optionality relationship, and providing a full example call with _apiKey that the schema examples don't show.

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 ('Get upcoming and recent earnings reports') and distinguishes the two operational scopes (single symbol vs. whole market). It is clearly separable from siblings like get_quote or get_company_news without needing to open the 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?

Provides clear usage context: pass `symbol` for one company, omit it for the whole market, optionally filter by date range, and a concrete example call. It lacks an explicit when-not-to-use or named alternative (e.g., release_calendar_markets for economic calendars), so it stops short of a full 5.

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