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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description adds genuinely useful behavior beyond them: the failure contract (verified=false means do not present) and that matching is character-level rather than semantic. It stops short of describing ambiguity or partial-match behavior.

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?

Two sentences, front-loaded with the purpose and the pre-condition, then the failure-mode routing to the sibling. No filler, no restatement of the tool name or title.

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?

With annotations carrying the safety profile and an output schema present, the description only needs to cover the invocation contract it does: input tolerance, success return shape, and the action to take on a negative result. Nothing an agent needs in order to call this 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% and the single parameter's format constraints (Tamil or English, at least two words / ten characters) are already documented in the schema. The description's "Tamil or English accepted" repeats that fact rather than adding syntax or edge-case guidance, so the baseline of 3 applies.

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?

"Letter-check a Thirukkural quotation against the canonical corpus" names a specific verb (letter-check/verify), the resource (quotation vs. canonical corpus), and the exact matching semantics. It is clearly distinguishable from the sibling kural_guidance, which fetches rather than validates.

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 states the timing explicitly ("BEFORE presenting or accepting it") and names the alternative path: when verified is false, do not present the quote but use kural_guidance instead. Both the when-to-use and the when-not-to-use branch are spelled out.

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