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

Goes well beyond the annotations by disclosing the destructive behavior in plain language ('silently OVERWRITTEN'), the per-file size limit, the managed-credential model ('never asks the user for a key'), and the fact that binaries don't land in Postgres. These are exactly the side effects an agent needs to reason about a destructiveHint write.

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?

The critical facts (destination, overwrite risk, size limit) are front-loaded, but the 'same reach the dashboard's Object storage explorer gives the owner' clause and the 'never stores binaries in Postgres' aside are padding at the edges of a five-sentence description.

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 parameter documentation, the description only needs to cover side effects and preconditions, and it does — overwrite semantics, auth level, and credential handling. The unquantified 'Per-file size limit applies' is the one gap an agent might trip on.

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 coverage is 100%, so much of the description's parameter prose (base64 encoding, extension sniffing for content_type, the key example) restates what the schema already documents. It adds no syntax, constraint, or format detail beyond the schema, 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 — 'Upload one file into the project's managed S3 bucket' — and situates it as 'the write half of the object-storage tools', which separates it from list_objects, read_files, and sync_files at a glance.

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?

Names the relevant sibling (list_objects) as the way to inspect an existing key before overwriting, and states the auth prerequisite ('Requires a read-write token'). It doesn't give an explicit when-not or a rule for choosing between upload_object and deploy_files/sync_files, so it falls short of a 5.

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