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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered; the description adds real behavioral context beyond that: page ordering, cursor-driven pagination, and empty-result semantics. It stops short of anything about rate limits or result caps beyond the page size, but for a read-only list tool this is solid.

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?

Front-loaded with what the tool returns, then arguments, then pagination behavior, then alternatives — a sensible order with no filler sentences. It is dense and slightly overstuffed for one paragraph, but each clause carries information an agent would otherwise have to infer.

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 an output schema (so return values need not be explained), full annotation coverage, and 100% schema description coverage, the description supplies everything else an agent needs: ordering, pagination loop, empty-result meaning, and when to prefer a sibling tool.

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?

Schema description coverage is 100%, so the schema already documents every parameter, and the description mostly restates it (limit 1-50/default 25, direction values, query matching, cursor source). It adds little beyond the schema, and it introduces a real inconsistency by calling all arguments 'optional' while the schema marks all four as required — an agent could misread the contract from either side.

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 ('List one page of calls'), its scope ('inbound and outbound merged'), ordering ('newest first'), and even the fields returned. It also names the sibling tools (getCallHistory, search) it is not, so an agent can separate it from app_getCall, getCallDetails, and getCallHistory without opening schemas.

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?

Explicit routing guidance: use getCallHistory for a compact list, use search to find a call by name/phone/topic, and use this for the paged Calls inbox view. It also gives the operational rule for pagination ('when nextCursor is not null, pass it as cursor to get older calls') and the terminal condition (empty list = no match).

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