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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds genuinely new context the annotations do not: that the call is free and that it returns a projection (shares received and fee) rather than performing a purchase, which anchors the read-only semantics to a concrete outcome.

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 tight sentence with the cost qualifier front-loaded, followed by purpose and output in order of relevance. No filler; every clause carries information.

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?

An output schema exists, so the description need not spell out return fields, and it correctly signals what comes back at a high level. For a one-parameter free quote tool with full schema and annotation coverage, this is largely complete, with only the missing explicit sibling routing leaving a small gap.

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 the single 'usdc' parameter is already fully documented including the USDC-6 pattern. The description restates the same convention ('2000000' = $2) without adding constraints or edge-case meaning beyond the schema, 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+resource (preview buying the tokenized stock basket) and names the outputs (shares and fee), so the agent knows it is a non-executing quote rather than the actual buy. The 'Preview' framing implicitly distinguishes it from the sibling stocks_buy, but it never names that sibling explicitly, so differentiation is inferred rather than stated.

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 leading 'Free.' and 'Preview' wording imply this is the zero-cost step to run before committing to stocks_buy, which is useful implied guidance. However, there is no explicit when-to-use/when-not statement and no alternative tool is named, so the routing logic is left to inference.

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