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

Beyond readOnlyHint=true, it discloses the ~15-minute delay, that it is not a live tick, that out-of-scope markets return `not_covered`, and even that the agent should state the quote time and delayed nature to the user. These are behavioral traits the annotations cannot express.

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 core definition, then scope, then exclusions, then follow-up guidance — a logical progression. Slightly dense with capitalized emphasis and a multi-clause final sentence, but no filler sentences; each one conveys routing or disclosure information.

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?

A simple 2-parameter read tool with no output schema and a readOnly annotation; the description still covers data staleness, market coverage, failure mode, and expected agent framing. Nothing an agent needs to call or explain this 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?

Schema coverage is 100% and both parameters are fully documented in the schema, so the baseline applies. The description adds only the 'US listings only' constraint on tickers and says nothing about the `context` parameter, which the schema already explains in detail. No additional semantic value beyond the schema.

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 and resource — 'latest traded price today' — plus the instrument scope (US stocks/ETFs) and the defining trait (DELAYED intraday ~15 min vs previous close). It explicitly distinguishes itself from the sibling price tools by noting 'every other price tool is END-OF-DAY (last close).'

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?

Gives a concrete trigger ('Use it when the user asks about TODAY during the US session') with example queries, an explicit exclusion (non-US listings return `not_covered`, use stock_prices instead), and a workflow pairing (stock_impact / search_news for the 'why'). The positive case, negative case, and alternatives are all named.

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