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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds a genuinely useful behavioral trait beyond that: rules are returned 'exactly as saved', signalling verbatim round-trip fidelity needed for update_segment. It says nothing about failure modes for an invalid ID or about pagination/size limits on large segments.

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 sentences, zero filler, and the returned-field list is front-loaded immediately after the verb. The trailing clause earn its place by explaining why verbatim rules matter.

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?

With no output schema, the description usefully enumerates the return payload, which is the main gap it had to fill. For a single-param read tool with full annotation coverage the definition is essentially complete; only error behavior for a bad ID is unstated.

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?

One parameter with 100% schema coverage, where the schema itself says 'Segment ID from list_segments'. The description restates the same sourcing hint without adding format, length, or validation detail, so 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+resource ('Show one segment's full definition') and enumerates exactly what comes back: name, match mode, lists, contact count and all rules. It also distinguishes itself from the sibling list_segments, which returns the collection rather than the definition.

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?

Gives a clear prerequisite workflow ('Find the ID with list_segments') and a follow-up use case ('so they can be passed to update_segment'), which is the read-modify-write pattern. It stops short of an explicit exclusion like 'do not use this to browse segments', but the routing is unambiguous.

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