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

Annotations already cover the safety profile (readOnlyHint, openWorldHint), so the bar is lower. The description adds real behavioral value by clarifying this is a metadata/discovery call whose output feeds a follow-up query ('valid history ranges and intervals'), though it says nothing about auth or rate limits.

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?

Two sentences, front-loaded with purpose and payload before the sibling routing. Every clause earns its place, with no restated name or filler.

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 an output schema present, return values need no explanation, and the description covers purpose, output meaning, and alternatives for a one-parameter read tool. Only minor gaps (whether ranges are paginated or how far back they reach) remain, and those are largely carried by the output schema.

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 coverage is 100% for the single 'symbol' parameter, so the schema already documents format and example. The description's 'one Yahoo Finance symbol' only reaffirms cardinality rather than adding syntax or semantics, so 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 (Fetch) and resource (chart metadata for one Yahoo Finance symbol), and names the concrete payload: valid history ranges and intervals. It explicitly distinguishes itself from three siblings, so an agent can tell it apart without opening a schema.

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?

Names three alternatives (yahoo_finance_ticker_history, yahoo_finance_ticker_quote, yahoo_finance_ticker_info) and the condition selecting each, which is strong routing guidance. It stops short of an explicit when-not for this tool (e.g., that it returns no prices itself), so it falls just under a 5.

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