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

The annotations already establish read-only, idempotent, non-destructive behavior. The description adds useful behavioral context beyond that: the default 48-hour lookback, the severity ranking scheme (critical/high/medium/low), and the set of event categories included. It does not discuss permissions, rate limits, or pagination, but those are somewhat covered by the schema/output schema.

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?

Two tightly written sentences: the first defines the tool and its content, the second defines when to use it. No filler or redundancy; the key scope is front-loaded.

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 annotations and an output schema covering safety and return format, the description is nearly complete for a simple read feed. One minor gap: it describes only the market-wide mode and omits the optional ticker-filter/watchlist mode documented in the schema.

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 schema already documents hours, limit, and tickers. The description only echoes the default 48-hour window and does not mention the tickers-based watchlist mode or add syntax details beyond the schema, so baseline 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 names a specific verb (Get), resource (market-wide activity feed), and enumerates included event types (board changes, insider trades, dividends, earnings, takeovers, price moves). Its 'market-wide' scope distinguishes it from company-specific siblings like get_company_changes or get_board_changes, but it does not explicitly name any alternative tool.

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?

It gives clear usage triggers: 'Use when asked what happened on the market, recent changes, market activity, or what's new across NZX.' This is good context, but no when-not conditions or named alternatives are provided.

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