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

Beyond annotations (readOnly, idempotent, non-destructive), the description discloses that the tool is free and explains the meaning of data_confidence, estimated_items, sources, data_version, and warnings. This is unusually rich behavioral context that helps an agent interpret results and understand projection uncertainty.

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?

The description is front-loaded with the core behavior and the meaningful distinction between no-argument and country-specific calls. It is dense but largely earns its length; the final response enumeration is somewhat long given that an output schema exists, though the confidence semantics add real value.

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 discovery tool with a simple one-parameter schema, full schema coverage, complete annotations, and an output schema, the description provides everything needed: what the tool returns, how to invoke both modes, and how to interpret confidence and warnings. Nothing critical 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?

Schema coverage is 100%, so the schema already documents the country parameter, including its role as country code or market MIC and the omit-to-list-all behavior. The description reinforces this with an example ('US') but does not add syntax or format details beyond what the schema provides, so the 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?

States a specific verb and resource ('Discover calendars') and precisely defines scope: no arguments returns all 250 countries and 30 markets, while a country code returns calendar metadata. This clearly distinguishes it from the date-computation siblings like compute_deadline and list_holidays.

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 clearly explains the two usage modes (omit country to list everything, provide country for details), which gives an agent enough to choose the right call pattern. It does not explicitly route the agent to sibling tools or state when to use this versus them, which keeps it from a 5.

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