dfm_index

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), so the bar is lower, and the description clears it: it discloses that data may be delayed, that the intraday open/high/low summary is computed client-side (i.e. not authoritative API output), that no API key is needed, and adds a not-investment-advice disclaimer.

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 purpose, followed by the return payload and then caveats, with essentially no wasted clauses. Minor slack from the slight 'Latest/newest' redundancy and the parenthetical '(no key)' interrupting the opening sentence.

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?

An output schema exists so return values need not be spelled out, yet the description helpfully summarizes them anyway; annotations cover safety and the description adds freshness, auth, and computation caveats. It could go slightly further on units/freshness granularity, but nothing needed to call a zero-argument tool is missing.

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?

The tool takes zero parameters, which is the baseline 4 case. The description correctly does not invent parameter semantics, and the empty schema with additionalProperties=false is self-consistent with the described no-input snapshot behavior.

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 names a specific verb ('Returns the newest index value') and a precise resource (the DFM General Index), and even enumerates the returned fields. It differentiates itself implicitly from quotational siblings like dfm_stock_quote by scoping to the index rather than a single security, but it never names an alternative explicitly.

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 by the resource scope (a market-wide index snapshot), and the parenthetical '(no key)' tells the agent no credentials are required. However, there is no explicit when-to-use guidance and no statement of when to prefer this over dfm_stock_quote or dfm_list_securities.

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