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

Annotations already declare readOnly, idempotent, and non-destructive behavior. The description adds value by specifying the exact scope ('every markdown file') and the output fields, which clarifies what the tool returns without contradicting the annotations.

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 a single sentence with no wasted words. It front-loads the action and resource, then appends the relevant output fields in parentheses, making it easy to parse quickly.

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 zero-parameter, read-only list operation with annotations covering safety, the description is complete. It states what is listed, the scope, and the returned fields; no additional information is needed for correct invocation.

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?

The tool has zero parameters and the schema is empty, so the baseline is 4. The description adds no parameter details, but none are needed; it instead describes the output characteristics, which is more useful for a parameterless tool.

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 ('List') and clearly identifies the resource ('every markdown file in the brain') plus the fields returned (relative path, size, last modified). This distinguishes it from siblings brain_read and brain_search, which imply reading or searching rather than enumerating.

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 phrase 'List every markdown file' provides clear context for when to use the tool: when the agent needs an inventory of all markdown files. It does not explicitly name alternatives or exclusions, so it stops short of a 5, but the intended usage is evident.

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

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds the scope of reading exactly one file and the relative-path constraint, but provides no details on error behavior or return format. These additions are consistent with annotations but minimal.

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 sentence with action front-loaded, a precise resource, and a helpful example. No filler or redundancy; every part earns its place.

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 tool with one required parameter, no output schema, and annotations covering side effects, the description is complete. The example and relative-path wording give the agent everything needed to call it correctly, and sibling tools provide surrounding context.

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 100% and the schema already describes 'path' as a relative path, so the baseline is 3. The description goes slightly beyond by giving a concrete example (decisions/2026-03-change-orders.md), which clarifies the expected format and nested structure.

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 the specific verb 'Read' with a clear resource ('one file from the brain') and a method ('by relative path') plus a concrete example. This distinguishes it naturally from siblings brain_list and brain_search without ambiguity.

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 implies usage—when you need the contents of a specific file by path—but does not explicitly contrast with brain_list or brain_search, nor does it state when not to use this tool. The context is clear enough but exclusions/alternatives are left to inference.

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

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

With annotations indicating readOnlyHint=true and destructiveHint=false, the safety profile is already clear. The description adds useful behavioral details: the search is literal and case-insensitive, and the tool returns source-citing output. However, it does not mention limits or edge cases like pagination or behavior with no matches, which would be extra context beyond annotations.

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 one focused sentence that front-loads the key distinction ('Literal, case-insensitive search') and immediately states the return value. Every word earns its place; no fluff or redundant restatement of the tool name.

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?

Given the tool is a simple read-only search with annotations covering safety and idempotence, the description is largely complete. The main missing context is the sibling differentiation and explicit behavior for the 'limit' parameter, but the tool's simplicity and annotations reduce the burden. It does not need to explain return values in detail because it already states them.

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?

The schema documents only the parameter names and types; description coverage is 0%. The description adds meaning by stating that the search returns file, line number, and matching line, which clarifies the 'query' parameter's effect. It doesn't explain the 'limit' parameter in detail, but a limit's purpose is fairly evident from its integer type and range. A score of 4 is appropriate because the description compensates for the schema's lack of semantic detail on what a query produces.

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 ('search') and resource ('the brain'), and explicitly states what it returns (file, line number, and the matching line). It clearly distinguishes itself from siblings like brain_list and brain_read by framing itself as a search operation rather than listing or reading.

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 implies this tool is for locating specific content within the brain, which is distinct from brain_list and brain_read, but it does not explicitly state when not to use it or name alternatives. The phrase 'Literal, case-insensitive search' gives some context on when it is appropriate, but it could more explicitly contrast with sibling tools.

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