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

readOnlyHint=true already declares the safety profile, so the description only needs to add context. It contributes the underlying endpoint (POST /v2/find_customer_with_phone), which is mildly useful, but says nothing about auth, rate limits, or whether a missing customer yields an empty result or an error.

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, front-loaded with the purpose and followed by the endpoint. Nothing is padded, though the raw endpoint path is arguably metadata noise rather than decision-relevant content.

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?

Simple one-parameter, read-only tool, but there is no output schema, so the description should say what comes back (single customer vs. list, empty result or error on no match). That gap is noticeable given the plural 'customers'.

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?

With one parameter and 100% schema coverage the baseline is 3, but the description genuinely adds semantics the schema lacks: matching is on the exact phone number, so partial or formatted variants won't work. The schema only shows example formats, not the matching rule.

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 and resource ('Find customers') and adds a scope qualifier ('exact phone number') that separates it from the broader list_customers and get_customer siblings. It never names a sibling or states when one should be preferred, so it falls short of a 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?

Usage is only implied: the agent can infer 'use this when you have a phone number' and that partial/fuzzy matches are excluded by 'exact'. There is no explicit guidance on choosing between this, list_customers, and get_customer, and no note on what to do when no customer matches.

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