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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the full safety profile is covered by structured data. The description adds only that it returns interest amount and final balance, which is largely redundant given the output schema exists; no assumptions, rounding behavior, or currency context are disclosed.

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?

Four short sentences, front-loaded with the operation and formula before the use cases. Slightly padded by the formula restating the tool's own name and the trailing bundle cross-reference, but there is no fluff.

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?

Wait – scoring on evidence: annotations cover safety, the schema fully covers inputs, and an output schema exists so return values need no elaboration. What remains (use contexts, a pointer to the finance-universal bundle) is present, making the definition sufficient for an agent to invoke it correctly, though it lacks sibling disambiguation.

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 all three parameters are documented in the schema (principal, annual_rate in %, years), so the baseline is 3. The formula I=P·r·t loosely maps the parameters onto the computation, but it adds little beyond what the schema already states.

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?

Names a specific verb ('Compute') and resource ('simple interest') and even gives the formula I=P·r·t, so the operation is unambiguous. However, with calculate_compound_interest and calculate_compound_interest_monthly among its siblings, the description never states how it differs from those near-identical finance calculators, so the sibling-differentiation bar for a 5 is not met.

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?

It gives positive usage contexts (short-term loans, basic savings accounts, homework), which is more than most siblings offer. But it never says when NOT to use it or names the obvious alternative (compound interest for anything with reinvested earnings), leaving the key selection decision to inference.

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