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

Annotations already declare readOnlyHint=true, so the safe read nature is covered. The description adds the requirement that exactly one identifier must be provided, which is a useful behavioral constraint beyond the schema. It does not disclose error behavior, return format, or edge cases (e.g., what happens if both are provided), but given the annotation coverage, a 3 is appropriate.

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, dense sentence that states the tool's purpose, the identifier options, and the exclusivity requirement. Every word earns its place, and no redundant explanation is included.

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?

The tool is a simple retrieval operation with all parameters documented and annotations covering safety. The description is sufficient for an agent to call it correctly. Minor gaps remain around expected return shape and behavior on invalid input, but these are not critical given the low complexity and the presence of readOnlyHint.

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%, so each parameter is already documented. The description adds meaningful cross-parameter semantics by stating that market_id and slug are mutually exclusive alternatives, which is not encoded in the structured schema. This goes beyond the baseline 3.

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 uses a specific verb ('Fetch') and a clear resource ('a single Polymarket market'), and explicitly names the two ways to identify it (by market_id or slug). It clearly distinguishes itself from sibling tools like polymarket_search_markets and polymarket_all_markets, which handle multiple markets.

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 instruction 'Provide exactly one of market_id or slug' is explicit usage guidance for the tool. It communicates the mutual exclusivity constraint clearly. However, it does not explicitly contrast with alternative tools or state when to prefer this over search or list tools, but the 'single market' framing implies the use case.

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