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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so safety is covered. The description adds genuinely useful non-schema context, namely the attribution obligation ('Data provided for free by IEX') and data provenance (release times from SEC EDGAR, statistics from PrintLine). It says nothing about behavior when a ticker has too few earnings events, or about the required-ticker mismatch implied by the schema.

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 use case and data description are front-loaded and tight, but the license paragraph is bloated: 'IEX Historical Data Terms of Use' is restated three times plus a URL, which is boilerplate repetition rather than agent-relevant content.

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?

For a single-parameter read-only tool with no output schema, the description conveys what is returned (day-1/day-5 move distributions) and the legal/provenance obligations. It could go further on sample size, metric shape (mean vs median vs range), and minimum history requirements, but nothing essential to calling it 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?

Only one parameter and schema description coverage is 100% (the schema itself documents the S&P 100 / NASDAQ-100 ticker restriction), so the baseline is 3. The description adds no extra ticker semantics such as case handling, symbol format, or what happens for out-of-index tickers.

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 precise resource: day-1/day-5 move distribution per ticker around SEC 8-K Item 2.02 earnings releases, which is unmistakably different from the macro/catalyst/status siblings. It stops short of explicitly naming or contrasting any sibling (e.g., get_catalysts, which also touches earnings dates), so routing is inferential rather than stated.

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?

'Use this when sizing an earnings trade' gives a concrete scenario for invocation, which is more than most definitions offer. There are no exclusions, prerequisites, or named alternatives, so an agent must infer that this is not a general price-history tool.

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