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

Annotations already declare readOnlyHint=true, openWorldHint=false and destructiveHint=false, so the safety profile is known. The description still adds real behavioral context: no live data fetch, rate must be above zero, amount may be zero or negative and is converted as given, no currency-code parameters, and an explicit list of what is out of scope (markups, fees, provider rounding). It stops short of describing output format beyond "converted.", which keeps it at a solid but not exceptional level.

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?

Front-loaded with the core definition and the sibling distinction before edge cases and non-coverage. The "Not covered" list is longer than strictly necessary for a two-parameter arithmetic tool, but every clause remains scoping-relevant rather than filler.

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?

Covers inputs, edge cases, sibling routing and scope exclusions well for a simple two-parameter tool. With no output schema, the return description is limited to one word ("converted"), leaving the response shape and any currency/label context unspecified.

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 baseline is 3. The description goes beyond the schema by warning about rate direction ("the rate that applies from the first to the second currency"), imposing the rate>0 constraint, and clarifying that negative or zero amounts pass through unconverted — meaning the schema does not carry.

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 ("Converts an amount between currencies using a manually supplied rate") and immediately distinguishes itself from the live sibling by naming it. An agent can select between the two without opening either schema.

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?

Explicitly names the alternative (workflow.run_forex_currency_converter_live) with the condition that selects it (rate fetched automatically), and gives a positive trigger ("Use when user already knows the exact rate they want applied"). Both when-to-use and when-to-use-the-other are covered.

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