Update call

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

Annotations already declare readOnlyHint=false, idempotentHint=true, destructiveHint=false, and openWorldHint=true. The description usefully clarifies that this only fills MISSING fields (partial, non-overwriting) and that results mirror place_call, which is consistent with the idempotent, non-destructive profile. It adds little else about auth, side effects, or limits, so it earns a moderate score against an already-covered annotation baseline.

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 tightly worded sentences with the core action front-loaded and zero filler. It is efficient, though the extreme brevity is arguably under-specification given the 24-parameter surface.

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 24 properties at 8% coverage and a mutation tool, the description is far too thin on inputs; it does not explain which fields are actually fill-able or their formats. It does offload return-value explanation to the output schema and place_call, but the input side remains largely unexplained.

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 8% across 24 parameters, so the description must carry the load and it does not: beyond 'missing_fields', it explains no parameter names, formats, or constraints. The result-shapes reference to place_call gives no input guidance, leaving the bulk of parameters undocumented in both schema and description.

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?

Names a specific verb and resource ('Fill missing_fields on a call') and adds a state precondition ('in needs_info'). It also ties output to the sibling place_call ('Same result shapes as place_call'), so the agent can tell it apart from place_call and cancel_call. It stops short of full sibling differentiation, so not 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?

The precondition 'on a call in needs_info' implies when to reach for this tool versus place_call (new call) or cancel_call, but it never explicitly states when to use it or when another tool is preferred. Guidance is inferable but not spelled out.

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