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

Annotations already declare destructiveHint=true and readOnlyHint=false, so the safety bar is lower. The description adds real value by spelling out the removal semantics (null deletes the current headshot) and the dependency on a prior upload, which the annotations alone do not convey. It says nothing about what happens to an existing headshot when a new one is supplied, which is the one remaining behavioral gap.

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 core action first and the null/removal case second. No filler, no redundancy, and the parenthetical maps directly to the parameter the agent must supply.

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 and full schema coverage, the description needn't explain return values, and it correctly covers both the set and remove paths. What's missing is only the overwrite behavior when a headshot already exists, a minor gap for a two-parameter mutation 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 both listingId and storageId are already documented, and the description essentially restates the schema's storageId text. Baseline 3 applies when the schema does the heavy lifting and the prose adds no new meaning.

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: applies an uploaded headshot to the contact card, with the null case explicitly defined as removal. An agent can tell this apart from set_logo and set_contact_card by the resource named. It stops short of naming a sibling to contrast against, so it lands at 4 rather than 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 description implies the precondition that the asset must already be uploaded (it says 'uploaded headshot') and covers the removal path via null. However, it gives no explicit when-to-use-vs-alternatives guidance, e.g. how this differs from set_logo or set_contact_card, leaving the agent to infer the boundary.

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