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

Annotations already declare readOnly/idempotent/non-destructive/openWorld, so this is safely a read. The description goes well beyond them: it discloses that yearHigh/yearLow are feed trailing-year (~12-13 month) figures rather than calendar values, that spot FX is closed Friday 17:00 to Sunday 17:00 NY time, and that a quote in that window shows the last close rather than a same-day move. These are real behavioral caveats an agent could not infer from annotations.

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-loads the one-line purpose, then groups the interpretation, trailing-year, and market-hours gotchas, each earning its place with no redundant restatement. Long but dense; every sentence addresses a distinct pitfall.

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 no output schema, the description carries return-value burden and does so: it defines yearHigh/yearLow, changePercentage's previousClose basis, and the meaning of priceAvg50/priceAvg200 relationships. Nothing material for correct invocation or interpretation appears 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%, so the baseline is 3. The description adds genuine semantic value by explaining the base/quote convention ('USDHUF 320 means 1 USD = 320 HUF') and how a rising rate relates to the averages, which the schema's terse 'uppercase with no slash' note does not. It stops short of adding format/syntax beyond the schema, so a 4 rather than 5.

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 ('Returns the real-time exchange rate quote for a forex pair') and immediately names the sibling to use instead for historical figures (get_forex_historical) and the broader list variant is implied by common pairs. An agent can distinguish it from get_all_forex_quotes and get_forex_historical without opening any 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?

Explicitly routes the agent: 'For a year-to-date or calendar-year change, a dated extreme or an exact 52-week figure use get_forex_historical.' It also explains the market-hours caveat that determines whether a quote is actionable. Clear when-to-use and when-to-look-elsewhere guidance.

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