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

Annotations already declare destructiveHint=true, idempotentHint=true, and non-read-only behavior. The description adds a real scope statement — only the target image field changes, other fields are preserved — but it never says whether an existing image on that field is replaced and is silent on the version-conflict behavior the schema mentions, which matters for a destructive operation.

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 short sentences with the verb and resource front-loaded, and the second sentence carries the scoping caveat. "Through the existing file upload" is slightly vague about where that upload came from, keeping it from a 5.

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?

For an 8-parameter mutation with an anyOf on record identification and no output schema, the description covers purpose and mutation scope but omits the record-lookup path and the version-conflict failure mode. The schema fills those gaps, so the definition is adequate but not self-sufficient.

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 explains id/record_id, version staleness, image/* mime restriction, and storage_key. The description adds only marginal meaning (a single image per call, sourced from an existing upload), so the baseline of 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 and resource: stores one image on an image field of a record. That distinguishes it from generic siblings like crm_update or crm_create. It does not explicitly name or contrast those siblings, so it stops short of 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?

"Through the existing file upload" implies a prerequisite (a prior upload producing a storage_key), which is useful context, but the description never states when to use this instead of crm_update or how to handle the id/record_id choice. Usage is implied rather than spelled out.

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