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 agent knows this is a safe, closed-world read operation. The description adds that the tool computes three outputs, but does not disclose error behavior (e.g., what happens with invalid inputs) or any other behavioral traits beyond what annotations provide.

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?

A single sentence that is front-loaded with the core purpose and then lists the outputs. Every clause earns its place with no redundancy or 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?

For a simple, pure-calculation tool with full schema coverage and annotations covering safety, the description is adequate: it states what is computed and what is returned. However, it does not mention potential error conditions (e.g., zero years) or provide guidance on rounding precision, leaving minor gaps for an agent.

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% with descriptive text for each parameter, so the schema already documents start, end, and years. The description adds the conceptual meaning that these are starting and ending values connected over time, but provides no additional syntax or format details beyond the schema.

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 (compute) and resource (compound annual growth rate), and specifies the exact inputs (start, end, years). It also names the outputs (total return percent, absolute change), distinguishing it from siblings like rule_of_72 or compound_interest which compute different financial metrics.

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 description implies usage for CAGR calculations but offers no explicit when-to-use or when-not-to-use guidance relative to alternatives like rule_of_72 or compound_interest. An agent can infer the appropriate context from the description, but no routing or exclusion criteria are provided.

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