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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. Beyond that the description adds no behavioral context: nothing about remote-service latency or rate limits, nothing about what a lookup yields vs. what requires a follow-up call, and no indication of fallback behavior when a source has no entry.

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?

A single front-loaded sentence with no filler, and the resource being looked up is named first. It is a dense enumeration, but every clause names a distinct source/capability rather than padding.

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, so return values need not be described, and the schema covers the 5 parameters including the nested _subject/_files record references. What remains missing is selection-aware context: how the source and query command interact, and how this tool relates to the many other protein-annotation siblings. Adequate, but only just, for a multi-source open-world lookup.

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%, and the schema itself carries unusually rich parameter semantics (command syntax, the 'plain UniProt search returns metadata only' caveat, the format=tsv fields=sequence workaround). The description only maps its prose source list loosely onto the source enum (and even omits complexportal and intact), adding little beyond the schema — baseline 3 is appropriate when the schema does the heavy lifting.

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?

The description gives a clear verb+resource ('Look up a protein') and enumerates the concrete data types reachable (UniProt records, domain architecture, interaction networks, expression, structures). It does not differentiate itself from nearby siblings such as lookup_gene, protein_profile, scan_protein_domains or lookup_residue_sites, so the agent cannot fully disambiguate from the text alone.

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?

Listing the capability per source implicitly tells the agent when this tool is the right one (need a domain architecture, an interaction network, an expression profile, a structure), which is more than nothing. However there is no explicit when-to-use, no when-not-to-use, and no named alternative among the many protein siblings.

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