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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, openWorldHint=false, destructiveHint=false). The description goes beyond them by disclosing what the response contains: buy/sell/mid values in Toman and a change-vs-yesterday field, plus a dual output form (rows and markdown). This matters because there is no output schema. It stops short of detailing row counts, ordering, or units for the change field, so it earns a 4, not 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?

The output shape is front-loaded and the whole thing takes one tight English sentence. The Persian restatement doubles the length, which is defensible for a localized tool but is still duplication penalty relative to a 5.

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 tool with zero required parameters and no output schema, the description covers what an agent needs: what comes back, in what format, with which price columns. Only minor gaps remain, such as row ordering and the exact meaning of the change column, which is why it is a 4 rather than a 5.

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 that codes is optional, its ISO 4217 format, pattern, and maxItems. The description only restates that codes can be enumerated. With a 1-parameter tool and a fully documented schema, the baseline score of 3 is correct.

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 the resource (rates board) and the two scopes precisely: all currencies, or the specific codes supplied. It also names the return shape (structured rows plus a markdown table), which separates it implicitly from get_rate; it never names a sibling directly, so it falls short of a 5.

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 whole board, or the codes you list" implies the when-to-use boundaries (bulk/batch retrieval vs a single rate in get_rate), and the schema confirms that omitting codes returns everything. However, no alternative tool is named and no exclusion or routing guidance is given, so the usage guidance stays implied rather than explicit.

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