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

With no annotations, the description carries the full burden, and it discloses the optional filtering and that it returns metadata. However, it says nothing about auth requirements, rate limits, or pagination, and the HTML-vs-JSON behavior is left to the schema rather than the description.

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 tightly written sentence that front-loads the resource (all supported currencies) before the optional filter clause. No filler or redundancy.

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 simple read-only listing tool with fully documented parameters and no output schema, the description is nearly sufficient. It could note return shape (JSON list vs HTML table) more explicitly, but nothing critical for calling it correctly 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 description coverage is 100%, so all three parameters (type, as_html, currencies) are already well documented in the schema, establishing a baseline of 3. The description restates the code/type filtering but adds no syntax or format detail beyond the schema.

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 (returns) and resource (metadata for all supported currencies) with scope (all, optionally filtered). It is clearly a currency-listing tool distinct from conversion/historical siblings, though it never names a sibling to sharpen the boundary.

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: use this to enumerate supported currencies, optionally narrowed by code or type. There is no explicit when-to-use vs an alternative, no prerequisites, and no statement of when not to use it.

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