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

Annotations only cover the safety profile (readOnly, non-destructive, open-world); the description adds the non-obvious behaviour: the URL is pre-signed and short-lived, auth headers must NOT be sent, and the missing-pack case returns { ok: false, error: "not_stored" }. It also documents pack conventions (metres, Y-up, rig pivot types and units) that no structured field conveys.

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?

Front-loaded with the core action and constraint, then broken into short scannable sentences covering auth, expiry, pack units, and the error case. The units/rig detail is arguably payload interpretation rather than invocation guidance, but it is dense and each sentence carries information.

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?

An output schema exists, yet the description still covers the failure shape and the semantic conventions inside the pack, which the schema cannot express. For a single-param read tool with full annotation coverage, nothing an agent needs to call or interpret it is missing.

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?

Only one parameter (slug) and the schema already documents it at 100% coverage, including its provenance from search_assets or get_asset. The description adds no further slug semantics (format, case sensitivity, behaviour on unknown slug beyond not_stored), so the 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: 'Return a short-lived signed URL for a catalogue asset zip (mesh, params, licence).' This clearly separates it from get_asset (metadata) and search_assets (discovery), so an agent can route without opening a schema.

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 concrete operating instructions — fetch with GET, omit API key/Authorization, share download_url with the user, read expires_at — and the schema ties slug back to search_assets/get_asset. It stops short of an explicit 'use this instead of X when Y' exclusion against siblings like get_model_mesh or get_asset.

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