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

Annotations already declare readOnly/idempotent/non-destructive/openWorld=false, so the safety profile is covered. The description adds context the annotations cannot: 'Free, no account needed' (auth requirement) and an enumeration of what gets returned (metadata, license, CDN urls, site links, related items, emittable source frameworks). It does not discuss failure behavior for an unknown id.

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 most decision-relevant fact ('Free, no account needed'), then contents, then usage. The middle enumeration of return fields is dense but each clause is informative; nothing is redundant with the schema.

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?

No output schema exists, so the description carries the burden of describing the payload, and it does so item by item, plus auth and usage context. The only omission is behavior on a missing or malformed id, which is minor for a single-item read.

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 the baseline is 3 and the schema already documents the id format. The description nudges above baseline by supplying a concrete example value ('object:adjustable_wrench') and by tying the id's provenance to search_catalog, which helps an agent construct a valid call.

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 ('Read one three.ws catalog item in full by its id') and names the sibling it complements ('from search_catalog') and the one it is not ('get_item_source'). An agent can distinguish it from search_catalog and get_item_source without opening any 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?

Explicit routing: 'Use this after search_catalog to inspect one result before you embed it; for paste-ready code call get_item_source instead.' It names both the precondition (after search_catalog) and the alternative with the condition that selects it.

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