mercury_update_recipient

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

Discloses that the tool writes persistently and only modifies passed fields. Mentions the exact endpoint path (singular vs plural) and specifies the return shape. Annotations are consistent; no contradiction.

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?

The description is well-structured with clear sections: main purpose, USE WHEN, DO NOT USE, SIDE EFFECTS, RETURNS. Every sentence is necessary and concise, with no wasted words.

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?

Covers the tool's purpose, allowed updates, exclusions, side effects, and return format. With no output schema, the return example is helpful. Lacks details on error handling or idempotency, but these are typical in API context.

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?

The description lists the updatable fields, matching the schema. It adds context that these are contact details and default payment method. Since schema coverage is 83%, the description supplements without redundancy.

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 clearly states 'Update an existing payment recipient' and lists the updatable fields. It explicitly distinguishes from adding a new recipient, especially for changing bank account numbers, which prevents misuse.

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 explicit 'USE WHEN' and 'DO NOT USE' sections. It gives a concrete use case (re-routing payments via different method) and directs to the sibling tool 'mercury_add_recipient' for prohibited changes.

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