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

The readOnlyHint annotation already establishes this is a safe, non-mutating operation, so the description's main added value is the "read replica" note, which usefully warns that returned data may be stale. It says nothing about result ordering, whether a missing match returns an empty set or an error, or how many rows come back by default.

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?

A single front-loaded sentence with the resource, the searchable fields, and the freshness caveat in that order. Every clause carries information and there is no filler.

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 simple two-parameter read tool the purpose is adequately covered, and the read-replica caveat is a meaningful addition. However, there is no output schema, so the description carries the burden of describing return values and it does not — an agent cannot tell whether it receives customer records, IDs only, or a count, nor whether results are truncated.

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 phrase "by name, email or account number" is a verbatim restatement of the query parameter's own schema description, adding no new meaning. With schema coverage at 50%, the description should compensate for the undocumented limit parameter, but it never mentions pagination, the default page size, or whether matching is substring versus exact — leaving half the parameters unexplained in both places.

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 names a specific verb and resource ("Search the customer directory") and enumerates the searchable keys (name, email, account number), so an agent knows exactly what the tool does. It does not need sibling differentiation here because none of the listed siblings (run_sql, whoami, read_file, etc.) overlap in purpose, but it also does nothing explicit to distinguish itself.

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?

There is no explicit when-to-use or when-not-to-use statement, and no alternative is named. The parenthetical "(read replica)" implies a condition — results may lag the primary record — which hints at when this tool is appropriate versus an authoritative source, but the agent must infer that on its own.

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