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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, so the description is free to add the genuinely useful traits: results are newest-first, sourced from the platform's own call log recorded as calls happen, and metadata-only with no audio anywhere. The one gap is pagination/cursor behaviour, which is left entirely to the schema.

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?

Three short sentences, front-loaded with the core action, then a usage cue, then a critical data-availability caveat. Nothing is redundant and nothing is buried.

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 an output schema present, return values need no explaining, and annotations cover the safety profile. The description closes the non-obvious risk (an agent assuming recordings are retrievable) and flags limited log history; only cursor-based pagination semantics are unaddressed.

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 only 20% (missed_only is the sole documented param), so the description carries real weight. It adds intent-level meaning for missed_only ('calls that need a callback') and clarifies ordering, but says nothing about limit, since, cursor, or direction — direction and limit are mostly self-evident from their names and enum, which keeps this from dropping lower.

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 recent WhatsApp voice/video calls'), plus the ordering ('newest first') and scope ('on this account'). It is clearly distinguishable from list_messages or list_conversations, though it never names a sibling explicitly.

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 one concrete usage cue: 'Use missed_only to find calls that need a callback.' There is no when-not guidance, no alternative tool named for broader history or per-contact lookups, and no prerequisites stated.

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