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

Annotations already declare a safe read (readOnlyHint=true, destructiveHint=false), and the description adds genuinely useful context beyond them: the access requirement of an FXMacroData API key and the exact failure mode for anonymous callers (subscription_required plus a subscribe link). It also warns that a successful capture is not evidence of full historical or speech coverage, which is important interpretation guidance.

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?

Three sentences, front-loaded with what the tool inspects, followed by the interpretive caveat and then the access requirement. No filler and every sentence carries distinct information.

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?

An output schema exists, so return values need no explanation, and the auth requirement/failure mode plus the coverage caveat cover the main operational concerns. The only minor gap is the absence of explicit routing guidance among the many calendar-related sibling tools.

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?

There is a single required parameter with 100% schema description coverage (ISO 3-letter currency code, case-insensitive, with examples), so the schema carries the semantics. The description only restates "for a currency" and adds no format or edge-case detail beyond what the schema already provides — the baseline 3 for high schema coverage.

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 ("Inspect") with a precisely scoped resource: persisted official-calendar captures, parser outcomes, configured sources, and coverage limitations for a currency. This is clearly a metadata/diagnostics tool, distinguishable in intent from siblings like calendar_snapshot or release_calendar, though no sibling is named explicitly.

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?

Usage is implied rather than stated: the agent can infer this is the tool for assessing how complete the archived calendar data is, and the caveat about successful capture not proving completeness hints at the interpretive context. However, there is no explicit when-to-use statement or routing to a named alternative among the several calendar-related siblings.

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