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

readOnlyHint=true already establishes the safe-read profile, so the description's added value is the explicit 'Metadata only; file bytes are not downloaded' constraint and the 'Returns {count, files}' shape. That is meaningful context beyond the annotation, though permissions or rate-limit behavior are not mentioned.

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 tight sentences with zero filler: contents first, then the scoping option, then the metadata caveat and return shape. Everything is front-loaded and earns its place.

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 no output schema, the description correctly supplies the return envelope ({count, files}) and the metadata-only caveat, and the rich schema covers pagination and filtering. Minor gaps remain around sorting defaults interplay and permissions, but the essentials an agent needs are present.

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 all six parameters (from, size, filter, related_id, sort_field, sort_direction) are already documented in the schema, including the pagination formula and the filter examples. The description restates related_id's purpose but adds no syntax or format detail beyond the schema; baseline 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 ('List file attachments') and enumerates the returned fields (filename, content type, size, file type, owning contact/job), which cleanly separates it from the sibling list_contacts/list_jobs/list_tasks tools. It also surfaces the underlying endpoint (GET /files).

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?

It hints at the scoping use case via 'optionally for one record (related_id)', but never states when to reach for this tool versus other list tools or when not to. 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.