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

Annotations already declare idempotentHint=true and destructiveHint=false, but the description adds real beyond-schema context: parts are concatenated in order with nothing inserted between them, re-sending a number overwrites that part, and the response includes length and SHA-256. It stops short of describing what happens if a part is skipped or how many parts total are allowed (the 400 max lives only in the schema).

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?

Three tight sentences, each carrying a distinct fact (identity, ordering/replacement behavior, return value) with no repetition of 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?

For a chunked-upload part tool the description covers the essential mechanics: ordering, replacement, and the returned checksum for verification. It would be fully complete if it pointed at the enclosing uploadId source (start_map_upload) and the follow-up finish_map_upload call.

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 67% and the description clarifies 'part' semantics (numbered, ordered, replaceable), which is useful. But uploadId has no schema description and the tool text never says where it comes from, leaving one required parameter unexplained.

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?

Names a specific verb and resource ('Stores one numbered piece of a chunked map upload') and situates it precisely in the chunked-upload workflow, which cleanly separates it from siblings like start_map_upload, finish_map_upload, and replace_map_content.

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?

The description makes clear this is a per-part operation within a larger upload and that re-sending a part replaces it, which is actionable guidance. It doesn't explicitly say to call start_map_upload first or finish_map_upload after all 400 parts, so the routing is implied rather than spelled out.

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