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

Annotations already declare readOnlyHint and openWorldHint, but the description adds genuinely new context: the cost ('Costs 2 request units') and the asymmetric default date behavior per view. It does not describe response shape or pagination, but with read-only annotations and no output schema the disclosure is above the bar.

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 resource type, then a tight view-by-view enumeration, then defaults, then format, then cost. Every sentence carries information, though the date-format and default-window statements partially repeat what the schema already documents.

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 four-mode, four-parameter tool with no output schema, the description covers per-view return contents, required-symbol conditions, default windows, date format, and cost. Missing only secondary details like ordering or result limits, which are unlikely to block correct invocation.

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, but the description adds meaning beyond the enum labels by explaining what each view actually returns and how 'from'/'to' default differently per view. It reinforces the SYMBOL.EXCHANGE format requirement for 'symbols', though that detail duplicates the schema.

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 the resource ('Market calendar') and then defines exactly what each of the four view modes returns (IPOs, earnings with actual/estimated EPS, earnings trends, split dates). An agent can tell it apart from the sibling 'splits' tool because the description says splits handles one symbol's split ratios. This is specific verb+resource+scope, not a restatement of the generic name 'events'.

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?

Explicitly routes the agent to the sibling tool ('For one symbol's split ratios, use splits') and states the prerequisite that trends 'requires symbols as comma-separated SYMBOL.EXCHANGE tickers'. The per-view default windows (today/seven days ahead vs. earliest split/no end) give concrete conditions for how to call each mode.

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