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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint. The description adds 'Read-only. No side effects. Idempotent. US only.', plus a 24-hour cache and verified source, providing extra context beyond annotations.

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 and front-loaded with purpose and usage guidelines. Every sentence provides value, though the feedback instruction at the end is a bit verbose but still useful. No redundant 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?

Given the tool's simplicity (one parameter, output schema exists), the description covers purpose, behavioral traits, parameter guidance, alternative tool, source, cache, and fallback feedback. It is complete and leaves no gaps for an AI agent.

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 schema already has 100% coverage with description for npi_number. The description adds an example and clarifies 'Do not include dashes or spaces', which adds slight value beyond 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?

The description clearly states the action ('Fetch'), resource ('NPI registration details'), and scope ('for a US healthcare provider by NPI number'). It distinguishes from the sibling tool compliance_search_npi_by_name, which is used when only the provider name is available.

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?

Explicitly states when to use ('when you have the exact 10-digit NPI') and when not to (use compliance_search_npi_by_name for name-based queries). Also provides formatting rules (no dashes/spaces) and indicates the parameter is required.

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