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

readOnlyHint=true already declares the safe-read profile, so the bar is lower. The description adds some value by implying the result may be any of three entity types (customer, contact, or business), which affects how the agent interprets the response, but it says nothing about multiple matches, no-match behavior, or case sensitivity.

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 short sentences with the lookup intent front-loaded. The trailing raw endpoint path is moderately useful filler and doesn't crowd out the substance, but it earns less than the first sentence does.

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 one-parameter read tool with no output schema, the essentials are covered: what it finds and the key input. The notable remaining gap is the return shape — whether the polymorphic result is a single record or a list, and what an empty result looks like.

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?

Only one parameter and schema coverage is 100%, so the schema fully documents it (type, length bounds, meaning). The description's 'has an email address' adds no syntax, format, or matching-behavior detail beyond that. 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 ('Look up') and resource set ('customer, business contact or business') keyed on email, which distinguishes it from the list_* and get_* siblings that take IDs or filters. It stops short of naming which sibling to use when you don't have an email, so it isn't a full 5.

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?

The condition 'has an email address' implies when to use it, but there is no explicit guidance such as 'use when you only have an email; otherwise use get_customer'. No exclusions or alternatives are named despite many overlapping lookup siblings (get_customer, get_business_contact, get_business).

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