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

Annotations only declare the tool as a non-destructive, idempotent read; the description goes well beyond that by disclosing computed behavior — CGST+SGST/UTGST vs IGST chosen from place of supply, state codes derived from GSTINs, invalid GSTINs flagged rather than rejected, HSN-wise summary, rupee rounding, and amounts in words. It also bounds scope (doesn't pick GST rates, doesn't compute cess), which the annotations cannot express.

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 trigger and output format, then capabilities, then exclusions — a logical order with no filler sentences. It is a single very dense paragraph with semicolon-chained clauses, which costs some scannability, but each clause carries distinct information.

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 16-parameter, zero-required tool this covers what matters: input modes, derived tax logic, rounding/word conversion, fallback handling, and explicit non-goals. Return values need not be explained because an output schema exists, so nothing an agent needs in order to call it correctly is 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 real meaning on top by naming the exact sub-fields expected for seller, buyer, and items, and by framing "details" as strictly a fallback for text that cannot be split. It doesn't explain the more nuanced flags (sez, reverse_charge, prices_include_gst, copies), leaving those to 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?

States a specific verb and artifact: converts pasted text or an uploaded bill photo into a GST invoice output as a PDF and Excel file. It names the exact output format, input modes, and the field structure (seller, buyer, items), so an agent knows precisely what it produces without opening the 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 an explicit trigger ("Use this when the user wants a GST invoice...") plus hard exclusions: not for export invoices, not for invoices outside India, not for invoices without GST, and not for e-invoices (IRN/QR) or e-way bills. Those alternatives/exclusions are exactly what an agent needs to route correctly.

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