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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=true and destructiveHint=false, so the safety profile is covered. The description adds genuinely useful method disclosure: it reads the latest SEC holdings report and screens every holding by industry and debt, and explains the UK-listing fallback strategy — behavior that goes beyond the 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 the core question front-loaded and no filler; each sentence carries information (recognition shortcut, US screening method, UK fallback). The final sentence is dense with examples but still earns its place by defining coverage boundaries.

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 only one parameter and no output schema, the description supplies the method, coverage and fallback behavior an agent needs to trust and select the tool. It does not describe the shape of the verdict returned (e.g., pass/fail detail or reasoning), which is the main residual gap.

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 the schema already gives ticker examples (VOO, QQQ, SPUS) and notes a Shariah fund name is accepted. The description echoes that input surface and adds UK ETF tickers, but adds little syntactic or format meaning beyond the schema, so the baseline 3 applies.

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+resource: answering whether a fund, ETF or pension fund is halal, and enumerates the accepted input classes (Shariah funds by name/ticker, US-registered funds/ETFs, UK-listed ETFs). This clearly separates it from siblings like screen_stock, check_crypto or check_medicine, which handle different asset/object types.

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 delineates the scope of what the tool will handle and the fallback path for UK-listed ETFs (via a US fund tracking the same index, or the index's holdings). It gives clear context for when this tool applies, but never explicitly names an alternative sibling or states when-not to use it.

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