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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds genuinely non-structured facts: ~15-minute delay on index and bond/commodity prices, snapshot-sourced vix/fear_greed/breadth, no AI cost, and universal tier availability. Data freshness and cost are exactly the traits an agent cannot infer from annotations or 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?

Front-loaded well: purpose, then cost/freshness, then detail. However, roughly half the text is a bulleted return-value enumeration that substantially duplicates the existing output schema, which is padding against this rubric.

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?

Freshness semantics, snapshot source for derived fields, tier availability, and cost are all covered, which is what an agent needs to decide whether the data is stale or accessible. The return-value block is redundant given the output schema, but nothing important is missing.

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?

The tool takes zero parameters and the schema is closed, so there is nothing to disambiguate; baseline 4 applies. The description correctly avoids inventing parameter guidance for a parameterless call.

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?

Opens with a concrete verb+resource framing ('Market health snapshot in a single call') and states it aggregates indicators that would otherwise need multiple calls, which separates it from per-stock siblings like get_stock. It does not distinguish itself from the closest neighbor, get_market_assessment, so an agent still has to guess between those two.

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?

'without requiring multiple tool calls' implies the aggregation use case, and 'Available to all tiers' removes an access precondition. But there is no explicit when-to-use vs get_market_assessment / get_market_movers / get_signals, so the routing decision is left to inference.

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