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

With no annotations provided, the description carries the full burden of behavioral disclosure. 'Query discarded' is a useful note about non-persistence, but it does not clarify what the tool actually returns, whether it has side effects, or that eight of the nine schema parameters are effectively ignored. The schema descriptions hint at 'discarded after the shape check' for other fields, but the tool description itself omits this and the overall behavior is opaque.

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?

The description is two short sentences with no filler. The primary action is front-loaded ('Count characters in a search query'), and the second sentence adds a behavioral note. It is appropriately concise, though the second sentence could arguably be integrated or expanded slightly with the output expectation.

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 has 9 optional parameters, no output schema, and no annotations, making it moderately complex. The description is far too minimal to be complete: it does not tell the agent which parameter to use, what the return value looks like, whether the other parameters are accepted but ignored, or provide any context for why the schema includes unrelated fields like url, city, feed, etc. An agent would likely be confused when trying to invoke this tool correctly.

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 the baseline is 3. The description adds the concept of counting characters in a search query, which aligns with the 'query' parameter's schema description ('Search text; discarded after the length check'). However, it does not explain the relationship between the stated purpose and the other eight parameters (ref, url, city, feed, host, json, path, zone), leaving their presence confusing.

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 states a specific verb and resource: 'Count characters in a search query.' This makes the core purpose clear and distinguishes it from sibling tools like memory-key-count (which likely counts keys) and hn-front-count. However, it doesn't explicitly state the output (e.g., returns the character count) or differentiate from a generic string-length tool, 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?

Usage is implied by the description: if an agent needs to know the length of a search query, this tool would be appropriate. But there is no explicit guidance about when to use this versus alternatives, no mention of prerequisites, and no exclusions. The context signals show many sibling tools, but the description does not help an agent decide between them.

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