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

Annotations already establish readOnlyHint, idempotentHint and destructiveHint=false, so the bar is lower. The description still adds genuine context beyond them: Regent checks policy and injects the credential so the key never reaches the agent, and the explicit 'nothing is changed / no money moves' reassurance for what is an FX-rate endpoint.

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?

Two tight sentences, front-loaded with the concrete endpoint and method restriction, with no filler. The closing 'Nothing is changed and no money moves' slightly restates destructiveHint=false but reads as deliberate assurance rather than padding.

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 5-parameter proxy read tool with no output schema, the description covers the essential behavior (credential injection, safety, allowed methods) and the base URL needed to interpret the path parameter. Parameter semantics for facts/intent/user_token rest on the schema, which is acceptable at 80% coverage.

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 80%, so the schema already documents path, facts, intent, method and user_token. The description only indirectly explains path by stating the base URL; it adds no format or syntax detail beyond the structured fields, 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?

The description states a specific verb (Read) and resource (the frankfurter.dev /v1/latest endpoint) proxied through Regent, and constrains the allowed methods to GET/HEAD/OPTIONS. It is clear this is the read-only variant of the paired sibling, though it never explicitly names lst-637408c1b10f to draw the contrast.

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 'GET, HEAD or OPTIONS only' clause is an implicit usage constraint telling the agent what class of operation is permitted. However, there is no explicit when-to-use guidance, no prerequisites, and no routing to alternatives such as the non-_read sibling or the other lst-* tools.

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