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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context: it automatically looks up data from SEC EDGAR + market data, and it computes both the fair-value ceiling and margin of safety. It doesn't disclose edge cases (e.g., missing data, negative EPS), but for a read-only calculator the description adds meaningful behavioral context beyond annotations.

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?

Three sentences with zero waste. The formula is front-loaded, the data sources and invocation mode are stated, and the alternative path is given in one sentence. Every sentence earns its place.

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 read-only calculator with 100% schema coverage and no output schema, the description is nearly complete. It explains the formula, data sources, both invocation modes, and the margin-of-safety output. It doesn't describe the output format or edge cases (e.g., what happens if ticker data is unavailable), but the annotations and schema cover the safety profile and parameters, so the description is sufficient for an agent to call it 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 the schema already documents all four parameters. The description adds semantic meaning by explaining the relationship between parameters: eps/bvps/price are used 'instead of a ticker lookup' and price is 'used to compute margin of safety.' This clarifies the two invocation modes beyond what the schema provides, though it doesn't detail validation rules or units.

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 ('Compute'), a precise resource (Benjamin Graham's fair-value ceiling formula), and the scope (US-listed ticker, margin of safety vs current price). It clearly distinguishes itself from sibling calculators like altman-z-score-calculator__compute_altman_z_score and dcf-calculator__compute_dcf by naming the formula and data sources.

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 'just pass a ticker' for automatic lookup, and explicitly states the alternative: 'You can also pass eps/bvps/price directly to compute it for a hypothetical company with no ticker.' This gives clear when-to-use guidance and distinguishes the two invocation modes. It doesn't name sibling alternatives, but the formula-specific scope makes the usage context clear.

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