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

Annotations already declare readOnly, idempotent, non-destructive, open-world behavior, so the safety profile is covered. The description adds real value beyond them: it explains that the ratio comes from the latest 10-K reporting interest income, that 'latest_annual_filing' and 'note' indicate staleness, and that purification cannot rescue a company failed by the business screen.

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?

Front-loaded with the core purpose in the first sentence, with no filler. The second sentence is dense with nested clauses and parentheticals, which slightly slows parsing but 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?

There is no output schema, so the description must carry return semantics, and it does describe both possible returns (ratio, and charity amount when dividend is given) plus staleness indicators. Remaining gaps like units/currency of the returned amount are minor.

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 both parameters are already documented, and the description adds only the conditional linkage that supplying 'dividend' yields a charity amount. It does not clarify currency handling (dividend 'in any currency') or how the ratio is expressed, so the baseline 3 is appropriate.

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-like outcome ('how much of a dividend to give to charity') plus the concrete resource (the purification ratio derived from interest income over total revenue). It is clearly distinguishable from siblings like screen_company, calculate_zakat, and find_halal_alternatives.

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?

Gives clear context for use: compute the purification ratio, and derive a charity amount when a dividend is supplied. It also flags the boundary case via business_screen for companies excluded by every standard. It does not explicitly route users away from siblings (e.g., when to prefer screen_company), so it stops short of full when/when-not guidance.

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