Index history

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

Annotations already declare readOnly/idempotent/openWorld, so the safety profile is covered; the description adds genuinely new behavioral detail about the response shape — `latest` is the newest value, `changes_pct` compares against 1, 5, 21 and 250 trading days back, and `points` are newest-first. It stops short of stating limits such as rate limits or behavior when days exceeds available history (~4,100), which is why it is not a 5.

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?

Three sentences, front-loaded with the core capability, then usage examples, then a compact field glossary. Every sentence carries distinct information and the sibling hand-off is placed last where it belongs.

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?

No output schema exists, and the description compensates by explaining the three return fields and their ordering. Combined with the fully documented 3-parameter schema and the annotation set, an agent has everything needed to call this correctly.

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 baseline is 3; the description earns above baseline by pairing parameters with concrete call patterns (days=250, days=2000 + step="monthly") that show how the knobs interact. It doesn't add index-selection semantics beyond the enum, so it stays below a 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 ("Get the daily history of a Fara Bourse index since 2009") plus the scope of what is returned (day/week/month/year change). It distinguishes itself from siblings by routing intraday/turnover needs to ifb_market_summary, so an agent can separate it from ifb_market_summary or ifb_history 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?

Gives two concrete usage scenarios with actual parameter values (days=250 for a year-to-date question, days=2000 with step="monthly" for a long trend) and names the explicit alternative (ifb_market_summary) for the intraday case. When-to-use and when-not-to-use are both covered.

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