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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive, so safety is covered; the description's 'Read-only' is redundant. It does add genuinely useful behavior: the exact return contract (basket, live index vs base, resolution source) and a strong anti-hallucination instruction ('NEVER fabricate a card's basket members or index value') that guards agent behavior.

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-loads the prerequisite and the core action, then the return contract, then the safety constraint. Dense but nearly every clause earns its place; the parenthetical '(register_agent, no key needed)' is slightly awkward phrasing but functional.

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?

With no output schema, the description correctly carries the return-value burden by enumerating title, summary, basket with weights, index performance, status, token/contract, resolution source, and URL. Combined with the auth prerequisite and anti-hallucination rule, an agent has what it needs; only explicit sibling routing is missing.

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 both parameters are already documented, including the query forms and the api_key source. The description restates the same three query forms ('title, EVCDX-* ticker, or id') with no added syntax, format, or partial-match detail beyond the schema, so baseline 3 applies.

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 (Explain/retrieve) and resource (EventTrader event card) and enumerates the identifier forms accepted (title, EVCDX-* ticker, id). It does not explicitly name a sibling it should be preferred over (e.g., trade_event_card, preview_card_basket), so it is clear but not fully differentiated.

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?

Prerequisite context is present via the api_key note pointing to register_agent, and the scope is 'ANY event card'. However there is no explicit when-to-use vs alternatives guidance or exclusions relative to siblings like build_custom_event_card or headline_event_card; usage is only implied.

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