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

With no annotations, the description carries the behavioral burden and discloses key constraints: maximum 93-day windows, chaining for longer spans, publication-day availability for tables 'a'/'c' versus Wednesdays for 'b', and data starting 2002-01-02. It does not mention auth, rate limits, caching, or return shape, but it adds substantial behavioral context beyond 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 description is compact and front-loaded: it opens with the core purpose, then presents the two query modes and key constraints. Every sentence contributes useful information without repetition 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?

For a six-parameter historical-series tool with a fully described schema but no annotations or output schema, the description covers purpose, mode selection, NBP's hard limit, publication calendars, and data start. It could say more about return format or caching, but it is complete enough for correct invocation.

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 description coverage is 100%, so the schema already documents code, table, last_n, start_date, end_date, and no_cache in detail. The description reinforces the two query modes and adds the useful chaining note for spans over 93 days, but most parameter meaning is already present in 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?

The description states a specific verb and resource: retrieving a historical time series of NBP rates for one currency against PLN. It clearly separates this from a current-rate or conversion tool through the phrase "historical time series," though it does not explicitly name sibling alternatives.

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?

It gives clear usage modes: either last_n quotes or an explicit start_date/end_date window, and notes that longer spans require chained calls due to NBP's 93-day limit. It does not explicitly compare this tool with siblings like nbp_exchange_rate or nbp_convert, but the operational context is clear.

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