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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, and the description adds a real behavioral constraint beyond them: the free-tier visibility window of yesterday/today/tomorrow in UTC, which affects what results an agent will actually get. It does not discuss pagination, rate limits or result size, so it stops short of a 5.

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?

One dense sentence that front-loads the resource and follows with scope and the free-key caveat; no filler. The tier limit is tacked on with a semicolon rather than being separated, but the size is appropriate.

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, no-required, read-only lookup with no output schema, the definition covers what it returns and the free-tier constraint, but leaves the coverage parameter's semantics and the practical default-window behavior unexplained.

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 75%: to, from and locale are described in the schema, but the coverage enum (19 categories) has no description anywhere. The description's 'central banks, statistics offices, earnings' hints at the coverage domain but does not explain the enum values, so it adds only marginal meaning.

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 resource (scheduled releases and decisions) with concrete examples of the event types (central banks, statistics offices, earnings) and the temporal scope (between two times). It is clearly distinguishable from siblings like get_change, latest_changes and search_changes, though it never names those alternatives.

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?

The description supplies a useful eligibility rule (Free keys see yesterday, today and tomorrow in UTC), which is genuinely actionable, but it gives no explicit when-to-use versus the sibling tools or any guidance on how to pick a date window.

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