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

Annotations already declare a non-read-only, non-idempotent mutation, and the description substantially adds to that: Kulhad cannot validate the address, duplicates are not checked, and the free plan permits only one active ID at a time. These are real behavioral and resulting-state facts an agent could not infer from the structured fields.

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, and each subsequent sentence (verification advice, no duplicate check, plan limit) carries distinct information. The middle verification sentence is somewhat long and reads partly as end-user advice, but nothing is redundant.

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?

An output schema exists, so return values need no explanation, and the annotations cover the safety profile. The description fills the meaningful remaining gaps (unverifiable address, duplicate acceptance, plan limits) for a mutation tool, leaving only the sibling-routing guidance unaddressed.

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 all three parameters (vpa, label, makeDefault) are fully documented in the schema. The description adds contextual framing ('for supporters to pay into') but no format or constraint detail beyond what the schema already supplies, so the baseline 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?

States a specific verb (Add) and resource (a UPI ID) plus its purpose ('for supporters to pay into'). The verb 'add' inherently distinguishes this from creation-adjacent siblings like update_upi_id, remove_upi_id, and set_default_upi_id without needing to name them.

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?

Provides an in-workflow verification instruction ('send one rupee... confirm it arrived before sharing the page') and a plan constraint, which implies the context for use. However, it never routes the agent explicitly to alternatives such as update_upi_id for changing an existing ID or set_default_upi_id, so tool-selection guidance is implied rather than stated.

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