Find the GST rate for goods

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

Annotations already declare readOnly, idempotent and closed-world, and 'Works offline' is consistent with openWorldHint=false. Beyond that, the description discloses the data currency model (all amendments applied up to the latest checked date), the exact contents of a result (rate, CGST/SGST/IGST split, notification and serial number, verbatim wording), and the multi-match caveat. It does not say what happens on a miss or how the future-dated amendment examples should be interpreted, which keeps it from 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?

A single dense paragraph that is front-loaded with source authority, then how to call it, then what comes back, then caveats. Almost every clause earns its place, though the parenthetical future-dated examples ('tobacco to 40% from 1 Feb 2026, psyllium exempt from 1 Nov 2026') read as noise that a reader has to decode rather than useful guidance.

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 3-parameter, no-output-schema lookup tool, the description covers source, currency, return payload and ambiguity handling well enough to call it correctly. The remaining gap is the undocumented limit cap and unstated no-match behaviour.

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 67%, so the baseline is 3. The description does add meaning for product — it searches the notifications' own wording rather than a product catalogue — and clarifies that both inputs can be combined, but it never mentions the limit parameter at all, which is the one parameter the schema leaves completely undocumented.

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 — official GST rates for goods — and names the exact source documents (Notification 09/2025 and 10/2025-Central Tax (Rate)). It also draws a hard boundary by excluding services (SAC 99xxxx), which separates it from the SAC-oriented sibling lookup_hsn_sac. It stops short of naming calculate_gst or lookup_hsn_sac as alternatives, so sibling routing is still partly inferred.

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?

The description gives two concrete invocation modes: pass an HSN code for every covering entry, or pass a product description to search the notifications' own wording. It also tells the agent how to handle ambiguity — several entries can cover one code at different rates, so explain the conditions rather than silently picking one. What is missing is explicit when-not-to-use guidance, e.g. that calculate_gst should be used to compute tax on an amount.

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