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

Annotations cover the safety profile (readOnly, idempotent, non-destructive), and the description goes well beyond them: record start date, carried-forward vs observed semantics, the 'never the next one' rule, the 14-day post-last-record cap tied to the gap ledger, and the gridError fallback. This is unusually rich behavioral disclosure.

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 purpose before the grid mechanics, and every sentence carries semantic weight rather than filler. It is dense and long, but the density is earned by the carried-forward rules that cannot be inferred elsewhere.

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?

There is no output schema, so the description must describe returns, and it does: each recorded rate, comparison rate, fees, and recording date, plus the grid shape. Combined with the parameter sourcing hints, an agent has everything needed to call it 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 the schema already documents all five parameters and the baseline is 3. The description adds genuine meaning beyond the schema by explaining what a grid point actually is (observed vs carried-forward, sourceDate, fill reason) and stressing that institutionId+productId form a pair, pushing it above baseline.

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 with scope: 'Advertised rate history for one product (institutionId and productId)' between two dates. It is clear what the tool returns, but it never names or contrasts with the closest siblings (rate_changes, rate_details, series), leaving the agent to infer the boundary.

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 some usage context: productId comes from find_products or compare_rates, and grid:true triggers the daily grid with a 367-day cap. However, there is no explicit guidance on when to choose this tool over rate_changes or rate_details, so the selection condition is only implied.

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