core

What every tool result looks like, and the limits it is held to.

Limits

Tool results consume model context. MAX_TOOL_CHARS limits one result. Factories accept the limit as mx because the model sets the budget.

# a grep answers with more rows than a search, because an exact match is cheaper to read
assert MAX_GREP_HITS > MAX_HITS
assert MAX_TOOL_CHARS < 8_000 and MAX_FILE > MAX_TOOL_CHARS
test_eq((MAX_TOOL_CHARS, MAX_HITS, MAX_GREP_HITS, MAX_API, MAX_FILE), (6000, 20, 60, 200, 2_000_000))

Every search backend returns a Hit with the path, line, symbol and matching text.

/opt/hostedtoolcache/Python/3.12.14/x64/lib/python3.12/site-packages/usearch/__init__.py:131: UserWarning: Will download `usearch_sqlite` binary from GitHub.
  warnings.warn("Will download `usearch_sqlite` binary from GitHub.", UserWarning)

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Hit

def Hit(
    path, line:int=1, symbol:str='', text:str=''
):

One search hit: path, line, symbol, text.

h = Hit('shalya/core.py', 12, 'clip', 'def clip(s, n=MAX_TOOL_CHARS, more=\'\'):')
h.path, h.line, h.symbol

('shalya/core.py', 12, 'clip')

test_eq(repr(h), "shalya/core.py:12  clip  def clip(s, n=MAX_TOOL_CHARS, more=''):")

Failure

Tool failures start with ERROR:. failed checks this prefix. Returning err(...) lets the model inspect a failure without ending the turn.

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failed

def failed(
    result
):

Whether a tool result starts with ERROR:.

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err

def err(
    what, e:NoneType=None
):

One tool failure, spelled the way every other tool spells it.

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host_err

def host_err(
    e
):

A caught exception, for a user-facing surface.

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HostError

def HostError(
    *args, **kwargs
):

A host refusal.

try: raise HostError('path is outside the open folders: /etc/passwd')
except HostError as e: shown = host_err(e)
shown

'HostError: path is outside the open folders: /etc/passwd'

test_eq(shown, 'HostError: path is outside the open folders: /etc/passwd')
test_eq(host_err(KeyError('nope')), "KeyError: 'nope'")
test_eq(err('could not read', HostError('no such file')), 'ERROR: could not read: HostError: no such file')
test_eq(ERR, 'ERROR: ')

try: json.loads('{not json}')
except Exception as e: msg = err('cannot read the edits', e)
msg

'ERROR: cannot read the edits: JSONDecodeError: Expecting property name enclosed in double quotes: line 1 column 2 (char 1)'

test_eq(failed(msg), True)
test_eq(failed('ERROR was not the problem'), False)
test_eq(err('no such file'), 'ERROR: no such file')

Clipping

clip truncates at a line boundary. clip_lines also reports the next line, which supports paging.

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clip

def clip(
    s, n:int=6000, more:str=''
):

Truncate a tool result to n chars. A caller with a way to resume passes it as more.

print(clip('one\ntwo\nthree\nfour\nfive\n', 12))

one
two
thre…[truncated: 12 of 24 chars shown]

test_eq(clip('short', 12), 'short')
test_eq(clip('one\ntwo\nthree\nfour', 12).splitlines()[0], 'one')

A line longer than the budget is truncated by character count. The notice reports the original and shown lengths without offering the same line as a resume point.

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clip_lines

def clip_lines(
    lines, start:int=1, n:int=6000, more:str='', empty:str='(nothing)'
):

Render lines within the budget, and say which line to resume from.

print(clip_lines(['def a(): pass', 'def b(): pass', 'def c(): pass'], n=30,
                more='read from line {next}'))

def a(): pass
def b(): pass
…[1 more line(s) not shown. read from line 3]

test_eq(clip_lines([], empty='(no matches)'), '(no matches)')
test_eq(clip_lines(['a', 'b'], n=100), 'a\nb')
long = clip_lines(['x' * 50], n=20)
assert long.startswith('x' * 19) and '50 chars' in long, long

Edits

Tool calls carry edits as JSON. cmds parses exhash commands. edits parses exact-text replacements. Both reject ambiguous input with an actionable error.

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cmds

def cmds(
    commands
):

Models emit JSON and exhash wants tuples, nested ones included: [[...]] becomes [(...)].

cmds('[["12|a1b2|", "s", "old", "new"], ["30|9f3c|", "a", "appended"]]')

[('12|a1b2|', 's', 'old', 'new'), ('30|9f3c|', 'a', 'appended')]

test_eq(cmds([['1|ab|', 'd']]), [('1|ab|', 'd')])
test_fail(lambda: cmds('{"not": "a list"}'), contains='must be a JSON list')
test_fail(lambda: cmds('["bare string"]'), contains='must be an array')

edits takes the exact-text form in any of its three spellings. apply_edits holds the refusals. Each one names the edit that is wrong and what to do about it. A match that is not unique needs more context. Two edits over the same span need merging.

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apply_edits

def apply_edits(
    text, es
):

Apply exact-text edits to text, or raise saying which one is wrong and why.

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edits

def edits(
    es
):

A JSON string, {'oldText','newText'} dicts, or [old, new] pairs: all three are unambiguous.

before = 'def greet(name):\n    return "hello " + name\n'
after = apply_edits(before, edits('[{"oldText": "hello", "newText": "howdy"}]'))
after

'def greet(name):\n    return "howdy " + name\n'

test_eq(edits([['a', 'b']]), [('a', 'b')])
test_eq(edits({'oldText': 'a', 'newText': 'b'}), [('a', 'b')])
test_eq(after, 'def greet(name):\n    return "howdy " + name\n')

The three refusals, on real text. Each message tells the model what to change rather than that it failed.

test_fail(lambda: apply_edits(before, [('name', 'who')]), contains='matches 2 places')
test_fail(lambda: apply_edits(before, [('nowhere', 'x')]), contains='not found')
test_fail(lambda: apply_edits(before, [('def greet', 'def hi'), ('greet(name)', 'hi(n)')]),
          contains='overlap')

Edit approvals carry a unified diff.

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diff_text

def diff_text(
    before, after, path:str='file'
):

Return a unified diff.

print(diff_text(before, after, 'greet.py'))

--- a/greet.py
+++ b/greet.py
@@ -1,2 +1,2 @@
 def greet(name):
-    return "hello " + name
+    return "howdy " + name

assert '-    return "hello " + name' in diff_text(before, after)
assert diff_text(before, before) == ''

Which tools write

Writes require approval. @writes marks a callable; WRITE_TOOLS provides the same fact when a caller has only its name. The tests require both representations to agree.

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summarise

def summarise(
    tool, args:NoneType=None
):

The imperative one-liner for a call: what a person would say they just did.

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summary

def summary(
    fn
):

Mark the one line a person reads after this tool runs. fn is given the call’s arguments.

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one_line

def one_line(
    v, n:int=90
):

One line of a value, short enough to sit in a list.

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has_effect

def has_effect(
    t
):

Whether t acts. Orthogonal to is_write: these are the effects approval does not gate.

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acts

def acts(
    f
):

Mark a tool that acts without writing a file the user owns.

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is_write

def is_write(
    t
):

Whether t is a tool that changes something.

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writes

def writes(
    f
):

Mark a tool as one that changes something. Approvals puts these in front of a person.

@writes
def create_file(path, text): return f'wrote {path}'
def view_file(path): return 'contents'
is_write(create_file), is_write(view_file)

(True, False)

test_eq(is_write(create_file), True)
test_eq(is_write(view_file), False)
test_eq(create_file.__name__ in WRITE_TOOLS, True)
test_eq(sorted(GIT_TOOLS), sorted(set(GIT_READ_TOOLS) | GIT_WRITE_TOOLS))