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

Annotations already declare readOnlyHint=true, openWorldHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds behavioral context beyond that: it specifies the output structure (about 49 ratios per period, stamped with report_period and fiscal_period) and the requirement that period is mandatory, with ticker or cik as identifiers. This is useful extra context about the data shape and invocation constraints, though it does not discuss pagination or limit behavior, which is acceptable given the output schema exists.

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?

The description is longer than average but each part earns its place: it lists key ratios, specifies the period stamping, states the required parameter, and gives usage guidance with an alternative. It is front-loaded with the core purpose and does not waste words, though the list of ratios could be trimmed for brevity without losing value.

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?

With an output schema present, the description does not need to detail return values. It adequately explains what the tool returns (ratios over time), the period requirement, identification methods, and the alternative snapshot tool. It does not mention pagination or limit behavior, but the schema has a limit parameter and the output schema likely covers structure. Overall, it is complete enough for an agent to call the tool correctly.

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 every parameter is documented in the schema. The description mostly reiterates what the schema already says: period is required, and ticker or cik can be used for identification. It does not add new meaning about parameter values or formats beyond the schema. Therefore, the baseline of 3 applies, as the description adds minimal extra semantic value.

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 clearly states it returns computed ratios for one company over time, enumerating many specific ratios (market_cap, enterprise_value, etc.). It also distinguishes itself from the snapshot sibling by noting the snapshot is one row and much smaller. This is a specific verb+resource description that allows an agent to understand exactly what the tool provides.

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 explicitly says 'Use it to trend a ratio across periods' and contrasts with the snapshot tool for current values only. This gives clear when-to-use guidance and names the alternative, leaving no ambiguity about which sibling to select.

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