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

Annotations already declare readOnlyHint=true, but the description adds genuinely useful context by resolving the apparent conflict that a POST is used for a read ('Castle takes the query in the body'). It does not discuss pagination behavior or result caps, which are left to 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?

Two short sentences, front-loaded with the resource and its contents, followed by the read-only/POST clarification and the endpoint. No wasted text.

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 5-parameter query tool with no output schema, the description covers what is being queried and why a POST is safe. It omits result-shape and pagination expectations, though the schema's results_size and page fields partially cover those.

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 filters, operators, query_type and paging are already fully documented in the schema. The description adds no parameter-level detail beyond the endpoint path, so the baseline of 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 and resource ('Query the security event stream') and enumerates the content returned (logins, registrations, transactions and their risk verdicts). It does not explicitly distinguish itself from the sibling castle_group_events, which is the nearest alternative, so it falls short of a 5.

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 gives no when-to-use guidance and never names an alternative such as castle_group_events. The useful hint about calling castle_get_events_schema first lives in the schema, not the description, so the description itself provides no routing guidance.

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