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

Annotations already declare this a safe, idempotent, read-only, non-open-world operation, so the bar for the description is lower. The description nonetheless adds real behavioral context: the ratio derivation (interest income over total revenue), the source filing, and the staleness disclosure via 'latest_annual_filing' and 'note' when the reported 10-K is out of date.

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 single dense sentence is front-loaded with the outcome and justified by the need to describe return values absent an output schema. It is slightly run-on, but every clause (ratio source, staleness fields, dividend output, business_screen caveat) 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?

With no output schema, the description carries the burden of describing returns and does so adequately: purification ratio, conditional charity amount, and named output fields ('latest_annual_filing', 'note', 'business_screen'). It is close to complete, though it never states units or how to interpret the ratio numerically.

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 both parameters (ticker, dividend) are documented in the schema itself, so a baseline of 3 applies. The description only adds that supplying 'dividend' triggers the charity-amount output, marginally extending the schema without new syntax or format detail.

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+resource: it computes a company's 'purification ratio' and the charity amount on a dividend. It is clearly distinguishable from siblings like mizan_screen_company and mizan_calculate_zakat, naming exactly the dividend-purification use case.

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 establishes when to use it (to determine how much of a received dividend to donate) and points to the sibling 'business_screen' for the excluded-business case via the referenced field. However, it does not explicitly frame this as an either/or routing statement, so the alternative guidance is implied rather than crisp.

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