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

Annotations already declare readOnlyHint, openWorldHint, and idempotentHint, so the safety profile is covered. The description adds valuable behavioral context beyond those: the 'cheap sequence-only' cost characterization, the toggle behavior for include_isoforms (alternatively-spliced sequences), and the output shape (length, parsed header). No contradiction with annotations.

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?

Four sentences, each earning its place: purpose/outputs, isoform parameter behavior, alternative tool, and input provenance + constraint. Front-loaded with the core action, no filler or repetition of annotation data.

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?

Given an output schema exists (so return format doesn't need restating), full schema coverage, and rich annotations, the description covers everything else: purpose, output components, param toggle, cheaper-vs-fuller alternative, input chain, and a handling caveat. Nothing critical is missing for a 2-param fetch tool.

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% — both parameters are fully documented in the schema (accession pattern + canonical-only instruction; include_isoforms default and behavior). The description adds minimal param-level value beyond what the schema provides, so the baseline of 3 applies. The isoform-stripping note is duplicated in schema, not new semantic info.

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?

Uses a specific verb+resource ('Fetch the canonical amino-acid sequence (FASTA) for a UniProtKB accession') and names the exact outputs delivered (sequence, length, parsed header). It explicitly contrasts with uniprot_get_entry ('full functional record'), clearly distinguishing itself from its sibling.

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?

Provides explicit when-to-use guidance ('This is the cheap sequence-only path') and names the alternative for full records (uniprot_get_entry). It also tells the agent where inputs originate (uniprot_search_proteins or uniprot_map_ids) and gives a concrete prerequisite instruction (strip '-N' isoform suffix) before calling.

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