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

With read-only and idempotent annotations already covering safety, the description adds substantial behavioral context: it enumerates the returned data, explains that basis marks pre-freeze numbers as hypothetical, and clarifies that only published benchmarks are available. It does not describe error behavior for invalid ids, but that is a minor gap.

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 front-loaded with the core purpose and then efficiently enumerates returned fields. The long first sentence is dense but earns its space because there is no output schema; minor improvement would come from splitting it for scanability.

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?

Because there is no output schema, the description needs to explain return contents, and it does so thoroughly: methodology rule, funds and weights, SEC series ids, expense ratios, and all computed statistics by window. It is nearly complete for a read-only getter, with the main omission being how an agent should discover valid ids.

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 0%, so the description must carry parameter meaning. It does so by explaining that the single required id can appear as 'etfiq-strategic-60' or 'strategic-60', giving useful format examples beyond the bare string schema, though it does not explain where ids come from or constraints on invalid values.

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 resource and scope: one ETFIQ benchmark in full, including its methodology rule, fund weights, and computed statistics. It distinguishes itself from broader tools by emphasizing 'one ... in full' and 'Serves the published benchmark only; it cannot be customised.'

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?

Usage is implied: use this to retrieve details for a known benchmark id. The description says it serves only published benchmarks and cannot be customised, which is a useful boundary, but it does not explicitly name alternatives such as list_benchmarks for discovering ids or compare_to_benchmark for comparison.

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