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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds the key behavioral trait that this is a pure, deterministic computation with no network fetch and a caller-supplied rate. It loses a point because 'Returns: converted' is an empty restatement rather than any useful detail about the result.

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 short sentences, front-loaded with the core behavior and the sibling routing. Every sentence carries weight except the trailing 'Returns: converted', which is filler and slightly dilutes an otherwise tight definition.

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 two-parameter, non-destructive, deterministic conversion with no output schema, the description covers the mode of operation and when to pick it. The only gap is that the return shape is not meaningfully described, though for a simple converter that is a minor omission.

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% and both parameters (rate, amount) are documented in the schema with directional semantics for the rate. The description adds only the 'manually supplied' framing, which does not extend the parameter meaning beyond what the schema already supplies, so the baseline 3 applies.

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 (Converts) and resource (amount between currencies) plus the defining constraint: a manually supplied rate, no live fetch. It explicitly names the sibling it is not (workflow.run_forex_currency_converter_live), so an agent can separate 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?

Gives an explicit selection condition ('Use when user already knows the exact rate they want applied') and names the alternative tool that should be chosen otherwise. This is exactly the routing guidance a sibling-heavy namespace needs, since many forex siblings exist.

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